Power to single brushless ARB compressor

[gbub]

I have installed my single brushless onboard air compressor. I installed the trigger wire directly to the AUX 6 switch without the ARB isolation switch. It works very well. However, I discovered the internal fan in the compressor continues to run (with the compressor off) after running the compressor a very short time. I am sure it is cooling the internals of the compressor which is fine, but that is another draw on the battery when the ignition is off. I don't know if installing the ARB isolation switch would stop that.

My greatest concern is if that fan comes on from heat soak from the engine. I don't want the fan running all the time. I may see if I can find some way to use the isolation switch to shut down all power to the compressor during times when I am not using it. Is this a bad idea?

I really don't want another drain source on the battery with the engine off. I don't like the fan running all the time either.

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[CalvinT]

I don't think it would come on for heat soak in the engine. The sensor would be internal to the compressor.

 

[Oilbrnr]

You're overthinking it. ARB is driving that fan for a reason independently.

 

[gbub]

Yes, I tend to overthink many things. I am an engineer.

I know ARB is has an internal fan for a reason, I just don't know if I agree with it running when the compressor is off. I also don't know if it will run with heat soak from the engine.

I will wait and see if it is running after a long drive. If it is running, I will figure out what to do then.

 

[CalvinT]

Yes, I tend to overthink many things. I am an engineer.

Then think like an engineer.

Think about what is the source of heat in the compressor. It's the compressor cylinder That's what is being monitored because that's what needs to be protected. Then attach a thermocouple to the cylinder and see what temperature the fan turns on and off. Then monitor heat soak temperature on the compressor mount after you've driven the Bronco but not run the compressor. That's what I'd do.

Start analyzing and stop guessing.

 

[Roger123]

Am I reading this right that the unit has a fan not run off the compressor? There is a separate electric motor to run a fan independent of the compressor? Just trying to get my head around the issue.

 

[CalvinT]

Am I reading this right that the unit has a fan not run off the compressor? There is a separate electric motor to run a fan independent of the compressor? Just trying to get my head around the issue.

The compressor has a large wire, probably 8 GA, directly from the battery to the compressor housing. That's always hot. The upfitter switch controls a relay that turns the compressor on. So it's possible to have a thermostat run a fan to cool off the compressor even though OP has turned off the upfitter switch.

The switch doesn't remove power from the compressor assembly. It just controls a relay that actually turns the comprossor on.

 

[gbub]

Then think like an engineer.

Think about what is the source of heat in the compressor. It's the compressor cylinder That's what is being monitored because that's what needs to be protected. Then attach a thermocouple to the cylinder and see what temperature the fan turns on and off. Then monitor heat soak temperature on the compressor mount after you've driven the Bronco but not run the compressor. That's what I'd do.

Start analyzing and stop guessing.

I like to keep things simple when I analyze. I agree the cylinder is the source of the heat. I am sure that is where ARB is measuring the temp. I don't want to take the compressor apart to obtain information. So, a thermocouple on the cylinder is not in my plans.

I mentioned before heat soak as part of my plan. Driving a short distance will not achieve the heat soak to the cylinder where the temperature is most likely measured for the fan control.

My simple test, as I mentioned before, is to drive the Bronco at highway speeds for an hour or more. That should achieve the heat soak to the cylinder. If the fan is not running at that point, I should have no reason to be concerned. I would do that as part of a trip I was doing and not just to run the test. That is real world information, not a guess.

 

[gbub]

Am I reading this right that the unit has a fan not run off the compressor? There is a separate electric motor to run a fan independent of the compressor? Just trying to get my head around the issue.

CalvinT is right. The fan is internal to the compressor and it runs independent of the compressor but does run off of the power to the compressor. It is there to keep the compressor from overheating when it is running. The fan also keeps running when the compressor is shut off. It runs until the compressor is cooled to a preset temperature.

My concern is the fan possibly running from heat soak from the engine. With the hot temperature under the hood, the fan would just circulate hot air and may run a long time after the engine is shut off. It is possible the fan does not draw a lot on the battery but it already has a lot of draw on it and I don't want even more.

 

[Johnny Mo]

I may not be 100% correct, but I also think that the compressor stays powered up. I run mine with an air storage tank so it tends to drop several psi overnight (ARB hoses - not happy with them) which for me would cause that to run and top off. I purposely powered my ign trigger to the rear power outlet but then went into forscan and changed the timeout from 60 minutes to 60 seconds - that gives the fan time to run and cool things off and then shuts it down so my compressor doesnt kick on every 8 hours to top off my tank.

 

[Aut-Lin]

I have the single brushless compressor set up in my engine bay and haven't experienced the fan coming on to cool off the compressor, with engine running or engine off.

 

[gbub]

I may not be 100% correct, but I also think that the compressor stays powered up. I run mine with an air storage tank so it tends to drop several psi overnight (ARB hoses - not happy with them) which for me would cause that to run and top off. I purposely powered my ign trigger to the rear power outlet but then went into forscan and changed the timeout from 60 minutes to 60 seconds - that gives the fan time to run and cool things off and then shuts it down so my compressor doesnt kick on every 8 hours to top off my tank.

My compressor will not run with the trigger wire turned off. It goes to AUX 6. There is still power to the compressor though. I discovered that by having my switch off when I connected the big red wire to the battery that powers the compressor. I got a beep letting me know it had power, but the compressor did not start until I turn the switch on.

 

[gbub]

I have the single brushless compressor set up in my engine bay and haven't experienced the fan coming on to cool off the compressor, with engine running or engine off.

My compressor fan stays on when I shut the compressor off after running it for less than 30 seconds. The fan does eventually shut off after running about another 5 minutes and that is with the engine off.

 

[Roger123]

CalvinT is right. The fan is internal to the compressor and it runs independent of the compressor but does run off of the power to the compressor. It is there to keep the compressor from overheating when it is running. The fan also keeps running when the compressor is shut off. It runs until the compressor is cooled to a preset temperature.

My concern is the fan possibly running from heat soak from the engine. With the hot temperature under the hood, the fan would just circulate hot air and may run a long time after the engine is shut off. It is possible the fan does not draw a lot on the battery but it already has a lot of draw on it and I don't want even more.

Yea, I had to go out and look at mine again. I had it in my head that the fan was turned by the compressor and not an actual separate fan driven by an electric motor.

In looking at the brushless manual (section 5.1.2) there is indeed thermo protection for the motor and it clearly states that the fan may run with the compressor off, i.e., not "compressing". I think yours is operating as designed. I do not believe adding the ARB switch would change that.

That may be a reason to not go with a brushless model if you live in hot climates or plan on underhood mounting. There is no discussion in the manual for the brushed model about the thermal protection. The brushless model uses more sensitive electronics to control/ run things and needs more cooling.

 

[gbub]

Your evaluation is spot on. I don't live in a hot climate but many of my adventure trips can get see very high temperatures. That is the main reason for my concern.

I still would like to be able to totally switch off the power to the compressor in these hot conditions. I would only do it when I don't need to use the compressor. If the fan runs do to engine heat soak, the fan would not cool the compressor anyway. I could still leave it on for a short time after running the compressor to get the temperature down some.

I am not going to do anything until I see if the compressor fan kicks in without running the compressor.

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