ARB Twin compressor wiring question

[mountain_rubicon]

Hey all, long time lurker here. I have a 2019 JLUR with the ARB twin compressor mounted under the hood with the GRIMM Offroad bracket under the brake master. A while back I was airing my 37s back up to street pressure from about 12psi after coming off the beach in North Carolina, and halfway through the last tire the compressor quit. No compressor, couldn't hear the fan, nothing. It was hot out, and even hotter under the hood. Like real hot. Quick google search seemed to confirm the compressor has a thermal shutoff. Thought ok, it needs to cool, I'll finish up later. Later came, still not working. Checked basic stuff I could do while on vacation, and found one of the two big 40amp fuses popped. Other looked good, but I replaced them both anyway. Compressor came back to life and all was good.

Got to thinking, if one fuse was good I should have had one side of the compressor working. Went out and pulled one fuse, switched it on, and had one side of the compressor function. Replaced that fuse and pulled the other, and the compressor didn't function at all.

Question is, is this normal operation? Seems like one fuse powers one side of the compressor, and the other powers the other side of the compressor plus the switch? Unit is only about a year old, so if there's a problem with it I want to get it sorted out before too long.

Also, anyone see any issue with doing away with the fuses and hooking the unit up to a circuit breaker? Would negate the problem of having to track down a Napa on vacation...

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[THAW]

No, it's not normal. Yes, the fuses are per piston.

I'd guess you have only one piston running even when both fuses are in place. In my experience, it's possible to hear the difference between 1 and 2 running pistons since they always seem slightly out of phase with each other. So, can you hear both running (i.e. do you hear a difference with both fuses in place compared to just the one working fuse holder)? If not, you likely have a bad wiring connection or a bad piston.

As for circuit breakers, I experimented with 40A Maxi Blade Solid State Circuit Breakers; they can work, but overheat way too easily in the weatherproof ARB fuse housing - now I carry them as a backup only. There are other types of circuit breakers, but in general breakers aren't ideal for hot engine bays.

 

[dstevens]

It's happened to me when it is hot. I've used the manual reset circuit breakers without a problem but only for a short period of time.

https://www.amazon.com/dp/B0BCT3M5JX

Otherwise

https://www.amazon.com/Bussmann-MAX40-Maxi-Fuse/dp/B000CF7CYA

 

[Terrymo]

ARB instructions have a pretty thorough step by step testing and trouble shooting section
https://store.arbusa.com/content/CKMTA12_Installation Guide.pdf

 

[SadRobot]

I know many people have had no problems with the Grimm mount but I had to move my ARB out of the engine bay because it kept blowing fuses. After contacting ARB their best guess was that the overheating of the compressor was blowing the fuses and they told me to move it somewhere cooler.

 

[mountain_rubicon]

I can definitely tell that both sides of the compressor are running when both fuses are installed. Its a very distinctive sound as compared to just the one. When I have a moment I'll grab an amp clamp and check each power wire independently just to confirm.

 

[mountain_rubicon]

Ok so quick update with info that could be handy for someone in the future.

Did some quick testing to have an idea what's going on with the compressor electrically. The control wiring harness provided by GRIMM plugs right into the factory harness so this should be all the same regardless of your configuration.

Control switch has three wires. One is ground, one is constant power, and one is control to the relay. The constant power is supplied by one of the two heavy gauge wires (the ones with the 40amp fuses). Pull the corresponding fuse, it kills power to the switch, and therefore the switch will no longer power the relay that turns on the compressor. So yes, this seems to be normal operation.

Also did a check on actual power draw on each wire with an amp clamp. The power wire that only ran one side of the compressor drew a peak of 28 amps at max pressure. The other power wire that ran one side of the compressor along with the switch and relay drew a max of 33 amps. This was measured with the compressor in a warm engine bay after about 45 minutes of engine run time, but with only a few seconds of run time on the compressor.

I found countless different wiring diagrams for setting up the compressor with different configurations, locker or air tank setups, mounting solutions, etc., but not any designed for trouble shooting the actual compressor, so hopefully this helps someone out in the future. Now I just saw ARB came out with a brushless version. Time to go resist the urge to take out the credit card...

 

[Terrymo]

I know many people have had no problems with the Grimm mount but I had to move my ARB out of the engine bay because it kept blowing fuses. After contacting ARB their best guess was that the overheating of the compressor was blowing the fuses and they told me to move it somewhere cooler.

Pretty sure someone has a a voodoo doll version of your Jeep somewhere. Anyone from your past come to mind when I say that?

 

[SadRobot]

Pretty sure someone has a a voodoo doll version of your Jeep somewhere. Anyone from your past come to mind when I say that?

Well I did get a great deal on my house because something about it being on an ancient burial ground? Not sure if related.




Obviously I’m kidding, there’s no such thing as a “great deal” on a house in Southern California.

 

[Terrymo]

Well I did get a great deal on my house because something about it being on an ancient burial ground? Not sure if related.




Obviously I’m kidding, there’s no such thing as a “great deal” on a house in Southern California.

Ok random question with no segue…do you guys still wheel with pigpen? I miss that guy on the forum. He always made me laugh.

 

[SadRobot]

Ok random question with no segue…do you guys still wheel with pigpen? I miss that guy on the forum. He always made me laugh.

He’s been busy at work. I did see him recently though after the engine got replaced he came by my house to pick up the engine hoist and stand he lent me.

 

[Terrymo]

He’s been busy at work. I did see him recently though after the engine got replaced he came by my house to pick up the engine hoist and stand he lent me.

Cool. I wish he could get out on parole here.

 

[THAW]

Ok so quick update with info that could be handy for someone in the future.

Did some quick testing to have an idea what's going on with the compressor electrically. The control wiring harness provided by GRIMM plugs right into the factory harness so this should be all the same regardless of your configuration.

Control switch has three wires. One is ground, one is constant power, and one is control to the relay. The constant power is supplied by one of the two heavy gauge wires (the ones with the 40amp fuses). Pull the corresponding fuse, it kills power to the switch, and therefore the switch will no longer power the relay that turns on the compressor. So yes, this seems to be normal operation.

Also did a check on actual power draw on each wire with an amp clamp. The power wire that only ran one side of the compressor drew a peak of 28 amps at max pressure. The other power wire that ran one side of the compressor along with the switch and relay drew a max of 33 amps. This was measured with the compressor in a warm engine bay after about 45 minutes of engine run time, but with only a few seconds of run time on the compressor.

I found countless different wiring diagrams for setting up the compressor with different configurations, locker or air tank setups, mounting solutions, etc., but not any designed for trouble shooting the actual compressor, so hopefully this helps someone out in the future. Now I just saw ARB came out with a brushless version. Time to go resist the urge to take out the credit card...

Interesting. Nice investigative work!

The one fuse killing all power makes sense now. I always forget the Grimm switch harness is different from the ARB switch harness (because I use the Grimm mount with a factory Aux Switch instead of the Grimm switch/harness).

The behavior is not normal for the standard ARB wiring harness.

The ARB harness is designed to pull relay/fan power from a separate vehicle ignition source; it doesn't use the 3rd wire (12V constant) on the compressor's control wiring connector. So, the behavior you discovered is normal for wiring harnesses designed to allow the compressor to operate independently of vehicle ignition, but not for the standard ARB harness.

I'm surprised the relay/fan power is an extra ~5 amps. I wonder if running that power over one of the fused ARB cables by using the Grimm switch harness is the primary reason there are reports of frequent fuse blowing with the Grimm mount.

 

[mountain_rubicon]

Interesting. Nice investigative work!

The one fuse killing all power makes sense now. I always forget the Grimm switch harness is different from the ARB switch harness (because I use the Grimm mount with a factory Aux Switch instead of the Grimm switch/harness).

The behavior is not normal for the standard ARB wiring harness.

The ARB harness is designed to pull switch/fan power from a separate vehicle ignition source; it doesn't use the 3rd wire (12V constant) on the compressor's control wiring connector. So, the behavior you discovered is normal for wiring harnesses designed to allow the compressor to operate independently of vehicle ignition, but not for the standard ARB harness.

I'm surprised the switch/fan power is an extra ~5 amps. I wonder if running that power over one of the fused ARB cables by using the Grimm switch harness is the primary reason there are reports of frequent fuse blowing with the Grimm mount.

It was really the most basic of electrical diags. I'm an auto tech by profession, I was just hoping to take the easy way out

It did seem as though 33 amps was very close to the fuse rating of 40. I know not best practice but I might forego the circuit breaker idea and up the fuse to 50 amps. If it's drawing that much power 10awg wire really doesn't seem sufficient, but that's what we've got so

 

[THAW]

It was really the most basic of electrical diags. I'm an auto tech by profession, I was just hoping to take the easy way out

I don't fault you for using the Grimm cable. I just wanted to point out to everyone that it's the reason the compressor completely shuts down when the one fuse blows. The same thing applies to the Epic Kraken switch harness, which a lot of people on the forum use (wisely, Epic fuses the switch power at 3A).

It did seem as though 33 amps was very close to the fuse rating of 40. I know not best practice but I might forego the circuit breaker idea and up the fuse to 50 amps. If it's drawing that much power 10awg wire really doesn't seem sufficient, but that's what we've got so

I agree about 10 AWG.

No comment on the 50 amp fuse

One question though: was the engine running when you read 28/33 amps on the power cables? I'm guessing, yes.

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