On board air - melting relays

[OSV]

The relay itself was not melting. The wire plug adapter hooked to the relay was slightly disfigured around one of the connections.

that indicates a connection problem, possibly but not necessarily undersized wire(the entire wire itself would get hot if it was really undersized), and not a melting relay... has a relay ever actually failed yet?

the specs for this compressor say that it already has a 30-amp inline fuse??? so i'm not sure about the benefit of putting a 40/50-amp fuse inline with a 30-amp fuse, the little fuse should blow first, perhaps someone thinks that the big fuse is somehow there to protect the relay, per the fuse location in this wiring diagram?? http://www.jeepforum.com/forum/f22/...k-dead-another-jeep-lives-1499894/index9.html

specs listing the 30-amp inline fuse: http://www.smittybilt.com/product/index/32.htm

 

[Buliwyf]

http://www.jmsonline.net/cole-herse...-2411701.htm?gclid=CLGt8Ierx84CFQaJaQodjcQBzA

 

[KSL22]

Power to the relay.


Wire to the pump.


This connection might have gotten warm as well.

 

[KSL22]

that indicates a connection problem, possibly but not necessarily undersized wire(the entire wire itself would get hot if it was really undersized), and not a melting relay... has a relay ever actually failed yet?

the specs for this compressor say that it already has a 30-amp inline fuse??? so i'm not sure about the benefit of putting a 40/50-amp fuse inline with a 30-amp fuse, the little fuse should blow first, perhaps someone thinks that the big fuse is somehow there to protect the relay, per the fuse location in this wiring diagram?? http://www.jeepforum.com/forum/f22/...k-dead-another-jeep-lives-1499894/index9.html

specs listing the 30-amp inline fuse: http://www.smittybilt.com/product/index/32.htm

Yes, the relays appear to have failed. I have not pulled them to test them individually. The wires included with the relay kit are undersized and that is not helping. I will check the auto parts store and grab the solenoid and wire.

 

[OSV]

it looks like a 30-amp, $4 relay:
https://www.amazon.com/dp/B0002KR9G..._m=ATVPDKIKX0DER&pf_rd_r=HW873XGQNB3278J1GGEC

just for drill, if you can pull the cover off of one, you can inspect it on the inside, see if anything looks or smells burnt... that burnt smell can be very helpful when troubleshooting electronics :-0

here is the tech page for that heavy-duty relay that the viking posted, it looks like littelfuse owns cole kersee these days: http://www.littelfuse.com/products/...nt-relays/continuous-duty-spst/24117_01.aspx#

i would also locate the 30-amp fuse that's supposed to be on the inside(?) of the compressor, so that you'll know how to change it out on the trail, if it blows, and also make sure that you have spares for it.

it looks like there is also an overheat circuit breaker on that compressor, which surely must be different than the 30-amp fuse that's listed for it.

 

[4x4junkie]

View attachment 361705
Power to the relay.

View attachment 361706
Wire to the pump.

View attachment 361707
This connection might have gotten warm as well.

It looks like there's at least two possibilities here, neither of which are likely to be the relay itself:
One is the possible problem of quick-connect terminals I mentioned earlier (basically what is used inside of that plastic socket). Occasionally you can get a little bit of corrosion on the connection, or a bit of looseness (both of which create resistance), and that is all it takes for it to burn up.

The other possibility is that the crimped terminal connection on the wire itself is what failed (and is more likely what I think happened). There are some people that will argue to the death that crimped terminals are the best thing since sliced bread, yet I have had numerous connectors do that very exact same thing to me too (one of which was on my ARB compressor). A new terminal & soldering it on fixed it for good every time.


What you can do to eliminate both of these possibilities is to cut that socket off and then solder the wires individually to the tabs of the relay (some of those relays are rated to 40A, so unless the relay has a rating stamped on it that is less than that of the fuse, or heat from the burning connection actually got into the relay and melted it too, there should be no problem with the relay itself).

However if you'd rather, get the continuous duty solenoid relay that was mentioned several posts ago, which would allow you to use heavier ring terminals over it's stud connections. Either way you'll be getting rid of that cheap plastic connector junk which should put this problem behind you.

 

[KSL22]

OKay, I rewired with 6ga from the fuse on the battery to a 12v solenoid. I shortened the wires from the compressor as much as possible and grounded the negative straight to the frame. Now it is going through 30a fuses. It will run about 20 seconds or so before popping the post battery fuse.
What else should I be looking at? The compressor worked fine running straight off the battery every other time I used it prior to attempting to make this setup. Nothing is hot before or after the fuse.

 

[4x4junkie]

OKay, I rewired with 6ga from the fuse on the battery to a 12v solenoid. I shortened the wires from the compressor as much as possible and grounded the negative straight to the frame. Now it is going through 30a fuses. It will run about 20 seconds or so before popping the post battery fuse.
What else should I be looking at? The compressor worked fine running straight off the battery every other time I used it prior to attempting to make this setup. Nothing is hot before or after the fuse.

In the Smittybilt installation instruction manual (.pdf) posted earlier in the thread it states the 2781 compressor has a 45 amp rated amperage draw (several here commented on it's 45A rating in their posts too). Shouldn't be any wonder why it's blowing 30A fuses, they are too small.

 

[OSV]

The compressor worked fine running straight off the battery every other time I used it prior to attempting to make this setup.

blowing 30 amp fuses/melting relay connections could be different symptoms for the same problem: an excessive current draw.

the spec page states: "Maximum amperage draw @ 120 psi" http://www.smittybilt.com/product/index/32.htm

it sounds like current draw goes up with resistance to airflow, so after only 20 seconds of use, what is the air pressure reading?

 

[ILIAN]

Yes, current draw does go up as head pressure goes up or airflow goes up. When it comes to this kind of applications it's better to overbuild the circuit for reliability. Smittybilt is not the best company out there and they may have screwed up stating that compressor can run with a 30 Amp circuit. In this case you should really go with at least a 40 amp circuit and a contactor. That way if you get a loose or bad connection down the road it's not going to give up the ghost at the worst moment. I would hook it up to a battery outside of the car with an ammeter and 6 gauge wires and no fuse and see how much it's drawing at maximum air pressure. Then wire it up so the circuit can handle a few amps more than the maximum draw. If it's drawing 35 amp at 120PSI you should wire it up for at least 40 amps. You can find a lot of cheap relays that are rated at 40 amps but they won't hold up to that for very long. Their contacts inside are very small. That's why for this application you need a contactor.

 

[chasespeed]

Okay.
The purpose of a branch circuit fuse, it to protect the wiring, and prevent fire in the case of a short, or overloaded conductor.
And the fuse is sized TO THE WIRE. Period if you have #8 wire, and use a 60amo fuse, the fuse is useless, and you might as well run straight off the battery.
But, you can de-rate the wire by running a smaller fuse.
If a piece of equipment requires a fuse, or additional fuse, it will be part of the equipment.
So, a number 8 wire would use a 50amp fuse(or smaller)' at the source of the power, preferably within 12".
So, your solenoid/constant duty relay/contactor(whatever you choose to call it), should be rated AT LEAST for 50amp. The rating of that unit, is for the contractors, springs, and coil. To be able to overcome the spring, when powered, and force the contacts apart when un-powered. That can become welded when over powered, even through starting loads.
There is voltage drop per foot of conductor.
This is worse as wire size gets smaller.
For longer runs, you upsize your wire.
This voltage drop, will also affect the load.
As voltage drops, amperage increased for a constant load.

In summary, if the compressor is under the hood, use #8 wire, and the proper switching device.
If it's 15+feet from the battery, use #6 and 80amp fuse.
And the fuse should be rated for low voltage dc.

 

[4x4junkie]

blowing 30 amp fuses/melting relay connections could be different symptoms for the same problem: an excessive current draw.

the spec page states: "Maximum amperage draw @ 120 psi" http://www.smittybilt.com/product/index/32.htm

it sounds like current draw goes up with resistance to airflow, so after only 20 seconds of use, what is the air pressure reading?

I already said why the compressor is blowing 30A fuses...

(trying this again):

http://www.smittybilt.com/docs/installation/2781.pdf

P/N: 2781
SPECIFICATIONS
Maximum Voltage: 13.8 volt
Maximum Amperage Draw: 45 amp
Maximum Restart Pressure: 150Psi
Maximum Air Flow: 160 L/min

Yes, there does seem to be a conflict of info on their web page, however I think it's because of an omission, not that it's "wrong" (the #2780 is the one rated @ 30A).



In the above .pdf there are also these two items:

Stopping and restarting: at high pressure can overload and blow the in-line fuse (Part #2780). At higher
inflation pressures, start the compressor and then attach to the filler to the tire valve stem. If you stop the unit
and need to resume inflation, remove the inflator tip from the tire valve, start the unit and reattach with the
unit running.

and

Resetting Circuit Breaker: (Part #2781)
The circuit breaker is located next to the on / off switch on the top of the rear housing. During normal
operation it remains in the down position almost even with the base. In the event of and overload it will popup.
If this happens, turn the power switch to off, disconnect the air hose and power cord. Push the breaker
down to reset and resume operation.

which seems to hint that only the 2780 comes with an inline fuse (30A) and the 2781 (what the OP has) uses a breaker instead because of the higher current draw.

 

[KSL22]

Thank you for all the response. I was away all weekend so I wasn't able to check in at all. It is at least 15' of 6 ga. from the battery to the solenoid. I will look online for a larger rated fuse holder. It is popping the 30a fuses right about 40-45 psi. for reference.

 

[proper4wd]

You likely had high resistance to ground before, so the compressor was not able to draw full power. Now that it's wired properly it is pulling the current that it should be and blowing the undersized fuse.

 

[OSV]

I already said why the compressor is blowing 30A fuses...

no, we told you that the specs clearly state that the max current draw is only at 120psi, and that the amount of current draw is load-related: "Maximum amperage draw @ 120 psi"

he's blowing 30 amp fuses after only 20 seconds of operation, so he's not drawing the max current that you claim is the problem.

is he drawing more than 30 amps after 20 seconds? possibly, but testing the current draw with an amp meter is problematic, because cheap multimeters are usually limited to 10amps max current, and he's certainly over that.

increasing the fuse capacity as you stated would be the simplest approach.

which seems to hint that only the 2780 comes with an inline fuse (30A) and the 2781 (what the OP has) uses a breaker instead because of the higher current draw.

they are both designed to run directly off of the battery, but there was no circuit breaker listed in the specs; crappy documentation leading to confusion, and i don't recall seeing the o.p. mentioning a circuit breaker either... i do see a circuit breaker in pics, next to the on/off switch, that's not on the 2780.

so the only reason that a fuse is needed by the battery would be to protect what's between the battery and the compressor... indeed, this genius hardwired a 2781 in with crimp connectors and no fuses :-/ https://www.youtube.com/watch?v=0mDY8Fxm1K4