Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 13, 2025 ...

Aux Compressor Issue

February 23, 2014, 01:23:46 pm

With the engine NOT running and low coach air pressure, the aux. compressor will run and shut off as one would expect. It shuts off around 100 psi. The on/off switch will control the compressor as it should. I can stop it while it is running.

Problem:
Now, with the engine running and building pressure, the aux. comp. comes on and runs. After a few minutes the high pressure relief valve starts opening every few seconds. The on/off switch has NO effect on the aux. compressor. It just keeps running and gets really HOT. When I shut off the engine the aux. compressor will finally stop. My coach pressure is around 115 psi or so .

So why does the aux. compressor run while the engine is running? I would not think they should run at the same time.
Why does the on/off switch not work during this time? It is like that circuit is bypassed when the engine is running.
What should the HWH air pressure be?
How do you adjust this pressure?

I reviewed previous posts on this same issue including the great video posted in Jan. 2013 showing the same issue as mine. He ended up adjusting the aux. comp. air pressure down a little to stop the high pressure blow off. I am not sure that is the root cause for my problem.

Dazed and Confused
 

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Re: Aux Compressor Issue

Reply #1 – February 23, 2014, 02:37:57 pm

Can't give you a good answer but this might help you understand system and what might be happening.

http://www.hwhcorp.com/Air_Suspensions_and_HWH.pdf#page=34

Keith

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Re: Aux Compressor Issue

Reply #2 – February 23, 2014, 02:46:34 pm

The small compressor has a pressure switch that opens about 90 psi, so if pressure is above hat area and compressor is still running, I would be looking at the pressure switch, mine is mounted on the compressor.
KISS thinking
Dave M

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Re: Aux Compressor Issue

Reply #3 – February 23, 2014, 06:07:28 pm

Thanks for the HWH  information.
I think my pressure is high. Can it be adjusted down by turning back the nut on the switch?
 

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Re: Aux Compressor Issue

Reply #4 – February 23, 2014, 09:18:12 pm

Keith - Thanks for posting the HWH doc link - I have added this to my doc file. 

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Re: Aux Compressor Issue

Reply #5 – February 23, 2014, 09:25:01 pm

We were at FOT last summer and one of the coaches compressor wouldn't shut off. He had pulled the fuse and everything else. Finally someone said turn off the HWH leveling. He did and the compressor quit. I think it was another 02 like ours.

There is apparently more than one circuit that turns that thing on.

Will be interested in what you find.

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Re: Aux Compressor Issue

Reply #6 – February 23, 2014, 09:36:29 pm

Similar issue here.  I had moved the coach last week to a driveway that was pretty much at the maximum of the leveling ability.  The system was struggling at the very end, trying to maintain the maximum extension of the passenger-side front airbags and it seemed to be taking all the compressor had...which was right at the relief valve limit.  So it would pump a little, then the valve would release, then it pumped again and the cycle repeated.  So I went and flipped my compressor switch and was surprised that it kept running.  A touch on the HWH system Air button stopped it.  So you are correct, at least in the 2002, there is more than one way for the compressor to be powered.

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Re: Aux Compressor Issue

Reply #7 – February 24, 2014, 11:14:24 am

From the HWH documentation:
"The port for HWH air leveling manifolds has no regulating valve or pressure switch. When ever a
manual or automatic raise function is performed, the HWH air leveling system controls send a +12 volt
signal to the air compressor relay. The compressor will run as long as the signal from the leveling controls is present."
This statement leads me to believe that under this scenario the comp. on/off switch is out of the circuit and only by shutting down the HWH system will the compressor stop.
I am still trying to figure out why the pop off valve lifts. It could be related to the above statement. I have only experienced this (compressor won't stop and the pop off lifts) when the engine was running.
Must be some kind of correlation there, like the coach air pressure is above the pop off limit, and that is what it is sensing.

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