Need help with minor electrical delimma

[fortel]

So I've got a 2012 Nissan Frontier that came with all the 12 volt power ports being switched so they're only hot when the key is on. I wanted one that was hot all the time so I picked up an OEM power port a and trim ring to put in the unused dash opening where the aux input would be if it had come with one. That was in early 2014. The circuit was run from my Blue Sea Aux fuse block and worked fine until recently. Started getting intermittent outages in the last year and finally it quit working at all a few weeks back. I checked the wiring and connections at both ends of the circuit and all seemed good so I ordered another power port from Nissan in case the first one had somehow failed.

Here's where I get lost. While I don't claim to be an expert on auto wiring, this is a really simple circuit. Power and ground on the Blue Sea are good and the other circuits on it (aux lighting) work fine. The fuse to the power port circuit is not blown, and I've tried swapping fuses just to eliminate that variable. When I check voltage at the power port with my meter I show that port having basically the same voltage as the switched power port below it when that one is hot. Nothing I plug into the added port (GPS, phone charger, etc) gets power but they all work in the switched port below when it is hot. I'm obviously missing something in my diagnoses, and probably something simple, but I need help figuring it out. Could the ground wire have lost continuity? The hot wire is obviously getting power to the first half of the circuit. I admit defeat and am willing to use it as a learning experience if someone has an idea what's going on. Thanks.

 

[aearles]

When I check voltage at the power port with my meter I show that port having basically the same voltage as the switched power port below it when that one is hot.

Am I understanding this correctly? You tested with a multimeter directly at the new 12v outlet inside the cab and it shows 12V+? Are you measuring both hot and ground from the outlet itself? A successful test there rules out anything upstream in the circuit, including failed connections, fuses, etc. Is the polarity correct? Your +/red should be the center pin and the -/blk would be the outer ring, which would cause your meter to register around 12V, if it's reading -12V then the polarity is backward.

Sounds more like the center contact pin isn't making complete contact inside of the outlet, but you said you replaced it altogether and it still doesn't work?

 

[fortel]

Thanks for the reply. Yes, when the red probe is on the center contact and the black probe is on the outer ring of the outlet I'm showing just over 12 volts and polarity is correct. What's perplexing me is that the power port I installed (and the replacement I put in yesterday) is the exact Nissan OEM port as the switched one below it. So the accessory plugs that make contact and work fine on the bottom port when it is hot should be making the exact type of contact on the port I installed since they are identical. And for 2-1/2 years the port worked fine before the intermittent outages started. I can't figure out what else to check.

 

[javajoe79]

If it is as you say and the port has power where it should and ground where it should but nothing works in that port, I am guessing your meter has an issue. Maybe its on hold with a reading from the other power port?

 

[fortel]

I don't think that affected the reading but to be absolutely sure I will check again this evening. I'm game to try any suggestions right now. Thanks for the reply.

 

[fortel]

The accessories I've plugged in to both outlets include my Garmin GPS, a USB adapter and a phone charger. All are powered when the bottom switched port is hot but none work in the installed port that is supposedly hot all the time. I would think the odds are pretty long than both one port would go bad and a new replacement would be bad out of the package. It would be easy enough to run new wiring from the fuse block but I'm measuring full voltage at the port now so I really can't see that being the problem. And if it was some third party aftermarket port where the internals were different I could maybe see that the contact points may not be lining up. But the installed port is the same OEM power port as the switched one below it so contact points, port design, etc. should all be identical.

I've got enough spare wire, inline fuse holders, connectors, etc so I may mock up a new circuit with the port I removed yesterday so I can mess with it without having to be in and out behind the dash.

 

[rayra]

what happens when you read good power in the unswitched port and then immediately plug in one of your devices?

 

[dwh]

You are checking at the back of the socket. Are you checking inside the socket as well? Putting the probe on the center inside?

 

[fortel]

So I didn't have much time last night to mess with the port since my son's scout troop began it's Monday night meetings again but I did make some progress. I double checked the voltage on both the switched and unswitched port and got basically the same voltage from each. Using some scraps of wire and connectors I made a test circuit using the port I originally installed (and had removed the other day thinking it might be bad). It all worked fine when powered up straight from the battery terminals. That made me start looking back at the wiring.

I used weatherproof heat-shrink connectors at each end of the wiring and they seemed fine, but when I checked the installed port again with the meter I got a dropped voltage reading of 8.3 which is quite a bit lower than when I checked it before. We had to go to the scout meeting at that point so I had my son drive and I took the meter and checked the port several times during the drive. I got varied voltage readings from 12.9 all the way down to about 4. So now I'm thinking its got to be a partial break in the wiring somewhere that is making/losing connection as it is bumped around. I don't remember any pinch points from when the wires were originally run and they go through the firewall inside of a rubber grommet so there shouldn't be any chafing at that point.

So my plan is to pull the old wiring and run new hot and ground wires from the Blue Sea fuse block to the port. I'm expecting that to fix the issue but since I have two open spots on the Blue Sea block I'll also move that circuit to a different position on the slim chance its an issue with that position on the block. I appreciate the ideas shared trying to run down the gremlin. I should (and hope to) be able to report back that the problem was solved.

 

[javajoe79]

Rather than running new wire you should check the power wire for a short to ground and ohm the entire length of wire.

 

[pugslyyy]

You need to check the voltage with the circuit loaded, because this problem is only happening when you try to pull current through it.

When you check open circuit voltage there is no current flow, so you read good voltage, but when you load the circuit there is a connection that is not allowing current flow. A lot of the time I see this at inline fuses, but could be elsewhere.

 

[fortel]

Thanks again for all the replies. I'll have time tomorrow evening to work on it some more. Again I'm a long way from being a whiz at some of this stuff but I want to learn. pugslyyy, what you said makes sense to me since nothing works as soon as it is plugged into that port. Its a fairly easy and short run from the Blue Sea block through the firewall and over to the dash opening, and since I already have everything on hand to run new hot and ground wires I think that is what I'll do next rather than trying to chase one connection at a time. I can't help but to believe that will fix the issue. And if so, then I can dissect the old wiring and try to see what went wrong after 2-1/2 years of it working fine.

 

[rayra]

what you describe is the fastest way to a fix, but maybe not the best. You apparently got something wrong the first time. It might be best in the long run and for your own edification if you take the time to track down where the error was. And it would help others to also avoid the same mistake.

I suspect a bad ground connection, myself, or a bad wiring connection somewhere. That's more likely than a damaged wire run right off the bat.

 

[fortel]

rayra

I plan on looking closely at the wires I pull (hopefully this afternoon if my schedule allows) to try and find the issue. I don't believe I got anything wrong the first time since the circuit worked fine for a little over 2-1/2 years before starting to give intermittent outages. My Blue Sea aux block has the negative bus built in so all my added circuit grounds go to that bus. All the other grounds are fine as is the 4 gauge ground wire from the aux block to the frame. The terminal connections on both the hot and ground of that circuit are tight. There could be a break in the wiring somewhere in the run I can't see or its possible that particular position on the Blue Sea block has developed an issue. The connections at the back of the power port were checked and changed when I tried the replacement port the other day so I don't believe the problem is there since the problem remained after changing those connections and the port. One thing I didn't think through and do on this circuit was leave a big enough loop of extra wire to be able to cut off the old connectors and make up new ones. I did think to do that on the aux lighting circuits when they went in later and will do the same with the new wires I run for the problem circuit.

With limited time in the evening to mess with it, the best course for me right now is to a) try switching the terminal connections at the fuse block to one of the two open spots on the block to rule out that the current position on the block has gone bad somehow, and if that doesn't make a difference, then b) pull the old wiring and run new, paying attention to if there are any crimps or chafes in the old wiring as I fish it out from behind the dash. Then when time allows I can dissect the connections on the old wiring to look for problems. I use the weatherproof terminals that both crimp and heatshrink. They have been dependable on the other aux lighting circuits but I can't rule out one of them has loosened internally somehow.

In the end I do want to figure out what caused the problem and learn from it. I appreciate the replies and all the suggestions have helped me to think through the components of the circuit and get a better understanding of where the problem may lie. I'll post back with what I find. Thanks again.

 

[rayra]

2-1/2yrs, ah, I'd thought it was a new run, thought you'd just added the port. That length of time is more than enough for chaffing or corrosion issues.