Power question involving my Dometic (Waeco) fridge (warning: LONG POST)

[Martinjmpr]

So let me start off by saying that my electrical knowledge is rudimentary, at best. Yes, I do have my HAM license and you have to know some stuff (Ohm's law, etc) but I'm banging my head here trying to figure this out.

OK, so let me start off with my issue:

Last year, following the DE-II in Moab, I decided I needed to get a fridge. I got a small one, a Dometic (Waeco) CF-18, which is a 19 liter fridge. My thought then was that the fridge would have stuff that I needed to keep cold (cheese, milk, meat) and that anything where cold was "nice but not necessary" (water, beer, soda) could go in a cooler.

That system worked out pretty well, however, I have had some "issues" with my Dometic fridge. Not that there's anything wrong with it, necessarily, just that it has some quirky features that I need to find a way to work with.

Here are the symptoms that have manifested themselves:

1. Plug the fridge into the 12v aux power socket near the tailgate of my 4runner (NOTE: Earlier this year I did the "jumper" modification to keep the 12v aux outlets powered all the time, so this gets power even when the ignition is off.) The 4runner has been parked for several days at this point (it's not my DD.) I put a bottle of warm water in the fridge to see how well it would cool overnight. Green light comes on (compressor on) but I'm also getting an intermittent red "error" light flashing (see below for description of this from the Waeco web site.)

2. Next morning, come out and check the bottle. Although the green light is on (with the intermittently flashing red "error" light), the bottle is warm.

3. Leaving everything connected, start the truck. Spend about 10 minutes with engine running hooking up the trailer. Drive trailer to trailer repair place to have some welding done. Turn off truck for about 10 minutes. After dropping off trailer, start truck up and drive to work, approximately 13 miles, maybe 25 minutes total. Turn off truck. Fridge is still plugged in to the REAR power outlet with error light intermittently flashing.

4. 11am: Come out to the truck to check the water bottle. It's nice and cold. Still having error light flashing, but it seems to be cooling OK. Incidentally, this has also been my experience on DE-III and on our recent camping trip to Canon City last weekend: Even if the error light is flashing, if the truck is running the fridge will work fine.

5. I also have a 12v plug with alligator clips that I can attach directly to the battery (bypassing the wiring.) I used this on DE-III. Usually when I had this connected to the battery, I got a solid green light with no flashing "error" light (although I did, sometimes, get the flashing error light, sometimes not. Typically if the truck is runnning or has been running for a while, the light is solid green. If the truck has been turned off for a while, the light is green with the intermittently flashing error light.)

6. Just to see if maybe the problem was the wiring to the REAR 12v outlet, last night I connected the fridge to the FRONT 12v outlet. The truck had actually been turned off for some time and yet, I got a green light with no “error” light flashing. Put the water bottle in and left it overnight. Next morning, checked it. Fridge cold, red “error” light flashing, and bottle so cold it had actually partially frozen!

Now, the above is the description of what is happening. Here's my theory on what is going on.

I don't know about the ARB, Engel, Norcold or other fridges, but one feature of the Dometic/Waeco fridges is the automatic cut off that is designed to prevent the battery from being discharged. Depending on the setting, it will cut power to the fridge when it detects a power drop, again this is to preserve the battery.

The web site for the Dometic/Waeco fridges says this:

With all DC refrigerators you must have enough voltage to run them properly, The battery in any vehicle can run your fridge just fine, even a small battery, but your must get all the voltage to the fridge not just some of it.

When running on a 12 volt car battery and with the switch on the fridge set to LOW (meaning lowest cut out battery protection voltage) the controller is very accurately set to cut off the unit to protect your battery if it sees less than 10.2 volts at the fridge. It must be understood that the voltage the fridge sees after it comes through the vehicle wiring and the cigarette socket not the voltage at the battery. You must deduct the voltages losses caused by your vehicle.

Regarding the intermittently flashing red error light, the FAQ says:

If the error light on your fridge flashes once every 5 seconds, it is definitely indicating that you have a voltage drop problem. This means that the wiring in your car may be inadequate to carry the correct amount of volts to the fridge.

The FAQ goes on to elaborate that

We have been receiving feedback from customers that the cigarette lighter in many vehicles, even some late model 4WDs is not adequate to the battery power correctly to the fridge, either the wiring is too thin or the cigarette lighter or accessory socket is dirty or has poor contacts. Both of these will create voltage drop and if it is enough, the computer in the fridge will see it as too low and turn off.

You can prove that there is absolutely no problem with any WAECO fridge by plugging it into an AC adaptor and you will see that it works perfectly, proving that it is in fact perfect. This is because the correct battery voltage is coming directly from the AC adaptor and is not loosing voltage by running through your car wiring or cigarette lighter socket. If the fridge stops after a few minutes and flashes the red low voltage warning light then your wiring is creating at least 2.5 volts loss. Battery voltage normally 12.2 with the engine stopped, less 2.5 volts loss in car wiring leaves only 9.7 at the fridge. So the fridge computer thinks your battery is flat and turns itself off to save it. It's that simple!

The solution is also simple! Replace the two wires from your battery to the cigarette light with thicker wire of at least 6 mm cross section (this does not mean 6mm thick it is just the way wiring is rated. Your auto electrician can sell you the right wire). An even better solution is to wire a special socket in the vehicle directly back to the battery in at least 6mm wire and you will never have to consider this problem again. The other advantage of a direct connection is that you do not need to have the vehicle ignition switch turned on to run the fridge. This is in fact another major cause of low voltage because when you turn the ignition to the accessories position, you can just imagine how many other things in your car are now also turned on and draining power. This also lowers the voltage available to the fridge in just the same way the lights dim in your house when something big starts up like and air conditioner.

SO, what I think is happening is this: When the engine of the truck is running[/B (and the alternator is being powered) the voltage is high enough to keep the fridge running even through the wiring that goes back to the 12v aux plug in the back of the truck. When I shut the engine off, there is still enough power to run it, but this power diminishes over time and if I leave the truck off long enough (like when I had the truck parked for 4 days without running it), it produces insufficient voltage, which the low-voltage detector in the fridge "sees" and this prevents the fridge from working.

Furthermore, my experience using the front 12v vs. the rear 12v seems to indicate that, as stated on the Waeco website, the wiring to the rear 12v outlet may be insufficient to carry the necessary voltage when the engine is not running (though it seems to do fine when the engine IS running, as my experience at DE-III confirmed.)

Obviously, one solution would be to do what Waeco suggests and either replace the wire to the rear 12v aux port with heavier wire. A second solution (again recommended by Waeco) would be to run a separate, direct connection from the battery to an extra 12v outlet in the rear of the 4runner (or wherever I want it, I suppose.) The drawbacks to doing this are that it would require me to disassemble the interior of the 4runner in order to conceal the wiring, which is both difficult and time consuming, as well as being able to run wires through the firewall without it looking like crap or being a fire hazard.

But my question (and here's where I'm soliciting advice and information) is this: Could I possibly cure this issue by simply upgrading my battery? IOW, if I go with a red top battery that's rated for a lot of amps, wouldn't this "fade" more slowly, possibly putting out higher voltage for a longer period of time? Does that make sense? Because if this is something I could fix with a better battery, that's something that is pretty easy for me to do and doesn't require any modification of the wiring.

My next question concerns using an AC adapter for this same fridge. Waeco/Dometic sells a very nice AC adapter for this fridge, it's called the EPS-50. The good news is I can get this from Amazon. The bad news is that it costs nearly $100 ($77 + $12 for shipping - it comes from an outside vendor, not Amazon so it's not subject to their free shipping benefit.)

As an alternative, I could look at a less expensive one, but I'm concerned that it might not work.

I tried a non-Waeco adapter once before and it did not work at all! But I can't figure out why it didn't work. Power is power, right? As long as the adapter is putting out sufficient amps, it should work, shouldn't it?

This, again, is where I'm getting confused, especially as to the specs of the fridge.

Here are the specs on the fridge (I downloaded this from an Australian Waeco web site): Rated current at 12vDC is 3.1A. Rated current at 24vDC is 1.9A.

Now, that seems reasonable, yes? Except that the sticker on the bottom of my CF-18 reads as follows: Power consumption: 12/24v DC: “7.0A,3.0A”

Can that be right? Why would the various manuals indicate a 3.1 or 2.something amp draw when the fridge itself indicates 7? And doesn't 7 seem excessive for a small fridge like this? (NOTE: I have to look for the manual that came with the fridge, I think it's in my garage somewhere, but I'm pretty sure it also said 7A draw.)

The EPS-50 (the expensive adapter made by Waeco for this fridge) is rated as follows: Input: 110/240v AC, output is 27v DC, 150w, 6A. Even though the manufacturer specifically says this will work on my fridge, I'm reluctant to spend the $$ to order it because if its rated output is 6A, then it probably won't work (at least, I don't see how it could, if the fridge is rated to draw 7A.)

OTOH, the much less expensive Schumaker PC-16 is rated as follows: Input: 110/120v AC. Output: 12v, 6a. No wattage output is included. I could look for a 10a 110v – 12v converter, but from what I've seen these aren't easy to find with the cigarette-lighter type socket. Seems to me if the 6A Waeco adapter will work there's no reason that the 6A Schumaker adapter won't.

[EDIT: Whoops, just saw my math error there. The Waeco adapter is rated at 150W, 6a - at 27v DC!, that means that at 12v DC, it is putting out 12.5A - more than enough to run a 7A fridge! (150w / 12v DC = 12.5A)]


BTW, I just bought a digital multimeter and will be voltage testing the outlets tonight, so stay tuned!

 

[pugslyyy]

I would simply run a heavier duty cable straight from the battery (with an appropriate fuse) to the back of your truck. Put it in split-loom and run it underneath the body, zip-tie it up out of the way.

 

[Finlay]

The best solution is for you to run dedicated wiring. Converting voltages is inefficient. Plus, if the voltage is too low at that point for the fridge, it might cause weirdness with your transformers, too. I know it's a pain in the ***, but that is the best solution.

That said, the Waeco inverter is 6A at 27v which is double what the stated draw of your fridge is at 24v. I suspect that those are peak (startup) amperages and that the nominal are a bit below that, hence the confusion.

Just to be clear - power consumed is simply volts times amps = watts. So, 12v at 3 amps is 36 watts, and at 24 volts would be 1.5 amps for 36 watts.

Anyway, that inverter (or pretty much any 12v ~6A) should work. Remember, though, that the inverter is powered at all times even when the fridge is not running, and will drain your battery much faster than the fridge alone would.

To answer your stated question - yes, you can probably upgrade your battery and resolve the problem. However, because the voltage drop down your line is constant, once the battery gets low enough for whatever reason (age, use, etc.) your fridge problem crops back up. So, at best, this is a workaround and not an actual solution.

 

[Rando]

As others have stated, the best solution is to run heavier gauge wires to the rear of the vehicle.

What tends to be the issue is the inrush current when the compressor on the fridge kicks on. This inrush current can be much higher (probably ~>7A in this case) than the steady state current consumption of the fridge. This higher current leads to more voltage drop in the wiring to the back of the vehicle, which causes the low voltage cut off to kick in. The low voltage cut off usually has some hysteresis built in, ie it will cut off the power at 10.8 (or what ever it is set for) but won't reconnect until the voltage is above 12.5v (or similar). This leads to the situation you are experiencing. When your main battery is down a little (say 12.3V open circuit) and assuming a wire resistance of 0.25 ohms, when you draw 7A at startup the fridge sees 10.6V and trips the LVCO. When it is running at 3.1A, you see 11.5V at the fridge, which is above the LVCO. When the car is running and the alternator brings the battery up to 14.4V, or if the battery is fully charged and at ~12.8V none of this matters. This is a common issue with the LVCO on inductive loads (I had the same issue with my edgestar fridge). I ended up modifying my LVCO to a lower cutoff, which you could also do.

Replacing the battery won't really help, it will just slightly delay the inevitable.

Another option, if you don't want to run new wires would be to disable the LVCO on the fridge and either risk running you battery down, or install a stand alone LVCO on the accessory circuit under the hood. This one would not see the voltage drop over the longer wires.

To answer your second question, any 12V DC power supply that can handle the load without drooping would be fine. For $100 you should be able to get a decent 12V @ 30 - 50A supply, which would have the advantage that you could also run your ham radio gear etc off it.

 

[Martinjmpr]

Another option, if you don't want to run new wires would be to disable the LVCO on the fridge and either risk running you battery down, or install a stand alone LVCO on the accessory circuit under the hood. This one would not see the voltage drop over the longer wires.

How would this even be done, though? Seems to me I'd have to get into the fridge and mess with the circuit board there, which I'm reluctant to do.

Since this is my first fridge, I have to ask, is this LVCO a common feature on other brands of refrigerators? Becuase I've never heard anyone else mention this issue with their ARB, Engel, Norcold, etc.

It's been a frustrating issue for me because of the apparent randomness and will it/won't it work issues, but a lot of that is my own errors, for example, putting the fridge in "high" rather than "low" mode. "High" doesn't mean high power, it means high LVCO setting, IOW, at "high' the LVCO kicks in at 11.2 whereas at "low" it doesn't kick in until 10.2 (it doesn't help that the manual is of no help in resolving this dilemma, since it appears to have been written in some weird language and then translated several times back and forth from English.)

So, slowly but surely I'm learning this but it's been a bit of a chore.

 

[dwh]

I think the Waeco's have a Danfoss compressor, which does a slow start and ramps up the RPMs. The Danfoss doesn't have a huge in-rush current like a typical compressor.


To the OP's question:

Yep, definitely a voltage drop problem.

As has been pointed out, volts x amps = watts. Thus, as the voltage of the battery drops (and the voltage of the entire circuit or loop drops), the amps required to supply the same 36w at a lower voltage goes up. That increase in amps, increases the amount of voltage drop. So as the battery voltage goes down, the amount of voltage drop goes up.

Putting in a battery with more capacity will delay the inevitable, but it won't change the situation.

I think your main problem really is that you are hammering your battery into the ground.

You let the rig sit for some days, running the battery down and then drive it only a little, which is enough to push the battery up to a surface charge of whatever your voltage regulator is set to (probably 14.2v or so). With that increased voltage, the voltage drop is not enough to cause the intermittent cut-out on the fridge.

But that's just a surface charge on the battery, not a full charge; it bleeds off quickly once the engine is shut down, and the battery is back to being way below fully charged. Letting a battery sit around at some voltage below full charge will shorten its life.

I'd say get a good battery charger to keep your truck battery topped off from shore power, that'll save the battery from an early death, and if it supplies at least 7a, then it'll also supply enough power to run the fridge when the truck is parked.

8a Battery MINDer would be my choice for that:

http://batteryminders.com/details.php?prod=12248

(You can probably find it cheaper if you look around.)

 

[Finlay]

Most fridges feature a LVCO. This protects the fridge, the battery, and the wiring. If I bought a fridge that didn't include one (and my bargain basement edgestar even does) I would install one inline with it for that reason.

I think Rando nailed what was happening pretty well.

So, slowly but surely I'm learning this but it's been a bit of a chore.

"Few educations are free" is what my grandfather used to say. :sombrero:

 

[Martinjmpr]

You let the rig sit for some days, running the battery down and then drive it only a little, which is enough to push the battery up to a surface charge of whatever your voltage regulator is set to (probably 14.2v or so). With that increased voltage, the voltage drop is not enough to cause the intermittent cut-out on the fridge.

But that's just a surface charge on the battery, not a full charge; it bleeds off quickly once the engine is shut down, and the battery is back to being way below fully charged. Letting a battery sit around at some voltage below full charge will shorten its life.

I'd say get a good battery charger to keep your truck battery topped off from shore power, that'll save the battery from an early death, and if it supplies at least 7a, then it'll also supply enough power to run the fridge when the truck is parked.

8a Battery MINDer would be my choice for that:

I guess I should elaborate: When I had the fridge running after the truck had been sitting idle, that was done specifically for the purpose of diagnosing my power/fridge issues. I do NOT normally keep the fridge hooked up (because, duh, I have a fridge at my house that works fine. Actually, I have two.)

Yes, it's true the truck often sits for days, though in fairness, it rarely goes more than about 4-5 days without being driven. While I do have a DD to drive to work monday through friday, usually on weekends I'm either going up into the mountains, pulling a trailer, or just going someplace where I want to be in a bigger, more comfortable vehicle, so I drive the 4runner. In fact, I often refer to my DD Mazda as my "weekday car" and my 4runner as my "WeekEND car." And it doesn't even have to be in the mountains, if the wife and I have to drive across town we'll either take her very nice 2011 Nissan Altima or my 4runner, just because my old Mazda is a bit threadbare and the AC doesn't work that well when trying to cool down two people.

So the 4runner does get driven. I have a battery tender on my motorcycle (which can go for weeks without being started) but I don't really think I need one on the 4runner.

 

[wrcsixeight]

I'll be restating a lot of what was written above with a few add ons. So no disrespect to the posters who I will be partially repeating.

Danfoss states in their compressor manual they do not want the power cord to use a shared bus or ground with any other device. They want the fridge hooked right to the battery, fused as close as possible to the battery. Not just for voltage drop purposes, they do not want power surges from other devices messing up the compressor controller. Since Waeco's come with a Ciggy plug and it is a major selling point, this is obviously not something they pass onto the customer, hoping it lasts longer than the warranty period.

So priority 1 should be a dedicated Ciggy plug over 10awg or thicker, wired to and fused at the battery.

Number 2 is the common misconception that every time the vehicle is driven, the battery is quickly and fully recharged. This is so far from true. Surface charge after running might hold the voltage in the 13's for a while, tricking somebody even savvy enough to measure battery voltage into thinking the battery is indeed fully charged, but surface charge can keep a battery 50% discharged above 13v for hours afterward, depending on battery health/design/brand.

Voltage is only a reliable indicator of battery state of charge on a rested battery, one which has not seen any charging or discharging current for several hours or longer.

Methods you might read about to remove surface charge are highly inaccurate and unreliable unless proven on a specific battery at a specific level of health, by measuring specific gravity of the cells or measuring the actual currrent consumption over a certain time. Too much effort. Don't trust the surface charge. Don't think that 5 minutes of turning the lights on reveals the true rested voltage.

Such a mistreated battery can still provide enough juice to start the engine, and the driver assumes that since it started the engine, it is fully charged. Wrong.
The longer and lower a battery sits below 80%, the more capacity it loses, and the faster it loses it. This capacity is not coming back, despite claims of magical battery desulfators or battery reconditioners and those that purchase them and want to justify their purchase. Topping off a battery by leaving any charger on it for an extended time is little different than putting a magical expensive "reconditioner" on it for several days. But there is a lot of my opinion in that last statement which will no doubt earn me some ire. So be it.

An aging battery is like a gas tank which keeps getting smaller. You can still fill it up, it just takes less to do so and has less to give afterward. There is no way to restore active plate material which has fallen to the bottom of the battery.

So in combination with an abused partially discharged and chronically undercharged battery, and too thin of wiring through too many connections, you have a fridge which sometimes works fine, and other times flashes all sorts of warning lights at you.

Do not rely on the alternator to fully charge a dead battery. The first 80% will likely take 6+ hours of driving, the last 20% can take another 6 hours. Use a plug in charger anytime you know you deplete the battery to any significant degree, and yes, using the stereo with the engine off can be a major battery drain, and your trip to the store and back is doing little if anything to replenish it. Idling to recharge is a true waste of fuel.

Best way to keep a Lead acid car jar battery healthy is to make sure you keep it fully charged, or as close to that ideal as possible, armed with the knowledge that the alternator and vehicle's voltage regulator were not designed to fully and quickly recharge a dead battery, but to keep a slightly depleted starting battery in the slightly depleted range or higher, and more importantly to not overcharge the battery, which can bring out the greedy lawyers.

Any AGM battery has a higher cold cranking amp rating than a similarly sized flooded battery. Many people assume this means the battery is more powerful and stores more energy. An Optima battery actually has about 30% less storage capacity than the same footprint rectangular battery, so in terms of powering a fridge, a new rectangular flooded battery could power the fridge for longer than the Optima.

Once again those that spend the $$$ for such a juicy battery will chime in with stories how well they perform for tasks which they simply can perform no better at, but some who have learned the hard way will hopefully chime in too.

If you are only running one battery to power this fridge, at least make sure it is a marine battery, which is a hybrid that excels at neither cranking a starter, nor recovering from deep discharges as well as a true deep cycle battery can, but is a compromise.

A true deep cycle battery can be used as a starting battery, but it must be significantly bigger to provide the same CCA rating as a starting battery.

Many AGM's like Odyssey claim to be fit for both duties, and I would get one of them before an Optima red yellow blue green or purple top.

 

[Rando]

The root problem is not really with the LVCO (although they could be designed better - ie the voltage has to be below a certain level for a longer period of time before they cut out) but with the resistance in the wires to the back of the vehicle.

I am not familiar with the wiring of your car, but it sounds like you jumped the accessory circuit under the hood to make it always on. You could splice a standalone LVCO into this jumper to disconnect the accessory circuits when your battery gets low. This would have the added benefit of providing an LVCO to anything you left plugged in (phone charger etc). They can be had for not much money:
http://stores.rogue-engr.com/-strse-1/1950-dsh-222,-LVD,-Low-Voltage/Detail.bok

How would this even be done, though? Seems to me I'd have to get into the fridge and mess with the circuit board there, which I'm reluctant to do.

Since this is my first fridge, I have to ask, is this LVCO a common feature on other brands of refrigerators? Becuase I've never heard anyone else mention this issue with their ARB, Engel, Norcold, etc.

It's been a frustrating issue for me because of the apparent randomness and will it/won't it work issues, but a lot of that is my own errors, for example, putting the fridge in "high" rather than "low" mode. "High" doesn't mean high power, it means high LVCO setting, IOW, at "high' the LVCO kicks in at 11.2 whereas at "low" it doesn't kick in until 10.2 (it doesn't help that the manual is of no help in resolving this dilemma, since it appears to have been written in some weird language and then translated several times back and forth from English.)

So, slowly but surely I'm learning this but it's been a bit of a chore.

 

[dwh]

So the 4runner does get driven. I have a battery tender on my motorcycle (which can go for weeks without being started) but I don't really think I need one on the 4runner.

Ah. Well, in that case, as long as you are driving enough to get the battery topped off (as wrc says - hours)...then what you need, is bigger wire.

 

[ebg18t]

Again this was mentioned by others, but you need to run better wiring to a dedicated plug. Engel recommends 10 gauge the whole way from battery to outlet to reduce voltage drop. Not to mention it is a lot safer. I believe ARB also recommends 10 gauge.

When I was trouble shooting issues with my Engel their most common issues are related to people running too small of wire to the fridge thus the fridge was cutting out do to voltage loss/drop

 

[86tuning]

Why not put a voltmeter on that wire to see what voltage you're actually getting to the fridge?

One measurement is worth a dozen opinions. Measure the voltage at the plug with the fridge running, and see what it is when you get the error light. Then measure your battery voltage at the battery itself. If there is a significant difference then you should probably upgrade your wiring

 

[wrcsixeight]

There is little doubt the voltage drop is the issue in my mind. I have a DC only front loading Vitrifrigo with a Danfoss compressor that pulls about 2.5 amps as the compressor speed is at the minimum. When I was insulating the cabinet where it resides, I powered it (as it was still stuffed with food and beer) by a longer route, basically about 30 feet, one way, of 12 awg and then an additional 10 foot 10 awg extension cord to the fridge. It ran all day fine, but when the sun was low and the battery voltage measured 12.8 or below, I was only getting 10.2v at the 10awg/12awg junction. The fan was turning on, but the compressor was not running. I'd could have wired up a LED light to the controller, and had I done so, I'm sure it would have been flashing the low voltage error code.

When I bypassed the 30 feet of 12awg and plugged the 10awg extension cord into a less convenient outlet closer to the batteries, it ran like a champ.

My stock dash mounted ciggy plug receptacle was wired with 18 awg.

Honestly If I had a chest type fridge, that ciggy plug receptacle would be cut off and a more substantial quick connector used in its place.

Ciggy plugs are a convenient standard, but they are a weak spring loaded connection, prone to heating, bad connections and voltage drop.

If your Waeco is running the compressor at max speed (3500 rpm)for initial cool down, then that is likely in the 6 to 7 amp range, and 7 amps is about the max a ciggy plug can handle for any length of time before it gets HOT.

Danfoss compressor speeds are controllable by the resistance in the thermostat circuit. The Waeco thermostat likely varies the resistance in this circuit where as on my fridge just came with a 270 ohm resistor to run it at 2500 rpm. I removed it so it runs at 2000, as I don't need faster cool downs. The slower the compressor speed, the more efficient it is. The faster the compressor, the shorter the duty cycle and the faster it can cool down items placed within but at the cost of increased battery draw and Peukert effect penalties.

 

[Martinjmpr]

Why not put a voltmeter on that wire to see what voltage you're actually getting to the fridge?

One measurement is worth a dozen opinions. Measure the voltage at the plug with the fridge running, and see what it is when you get the error light. Then measure your battery voltage at the battery itself. If there is a significant difference then you should probably upgrade your wiring

Good point. So I got a digital multimeter and tested both sockets after the truck had been sitting, not running, for a day or so. Measurement came out to ~12.5 to 12.8 volts. Of course, when I started the truck, that jumped up to 13.5, which I guess is the running norm.

So here's a dumb question: How can I measure the voltage when the fridge is plugged in? The power plug fills the socket, which doesn't give me a way to measure the voltage the fridge is receiving.

I guess since there are two 12v power connections and they are on the same circuit, I could plug the fridge into one and then use the multimeter on the other one. But, let's say I plug the fridge into the front power plug and measure the voltage at the rear - would that give me an accurate measure of the voltage drop between the front and rear?

If your Waeco is running the compressor at max speed (3500 rpm)for initial cool down, then that is likely in the 6 to 7 amp range, and 7 amps is about the max a ciggy plug can handle for any length of time before it gets HOT.

Ah, I hadn't thought of this but it makes sense. More energy is required to cool down intially than is required to maintain the cool temp. Most of my "tests" have started off with a warm fridge.

So for those who say "run bigger wire", who here has done this and what is involved? I presume that at the very least I'll have to remove a bunch of interior body panels since the wiring is concealed inside the interior trim. Anyone done this on a 4th gen 4runner?

Here's another thought/idea/question: I see some folks running something like an auxiliary power block (like a Blue Sea fuse block) that is attached the battery. Now, I don't think I really need something like that as I already have a set of auxiliary lights that are wired in to where my fog lights used to be, and I have no desire currently to run any more lights so I don't think I need a multi-input fuse block. But I'm wondering if I could run a dedicated wire from the battery but put in a switch under the dash that I could switch off when not needed, and then run these wires back to the rear of the truck for the fridge? Anybody done something similar? And what kind of waterproof/dust proof switch would be a good one to use? Reason I ask is because if I'm going to end up replacing wires throughout the whole truck, I might as well just run a new, dedicated wire, right? It seems to me it'd be the same amount of work.

So here's the next data point: I went to Gander Mountain and bought a 120v AC to 12v DC converter because it is considerably less expensive than the Waeco power converter. Plugged it in, and the power lights came on the fridge, but while the fan ran, the compressor did not and it never warmed up. Interestingly, the low voltage error light never came on, but neither did the green "compressor" light.

I think at this point I'll just bite the bullet and spend the $$ on the Waeco adapter so when we're at a fixed campsite with 120v AC power I can run the fridge off that.