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Topic: 1992 ORED Air Compressor Always On (Read 587 times) previous topic - next topic

1992 ORED Air Compressor Always On

1992 ORED, hydraulic brakes.  Front air compressor runs whenever the engine is on.  What is this thing for?

Re: 1992 ORED Air Compressor Always On

Reply #1 –
Quote from: Paul GA –
Front "air compressor" runs whenever the engine is on.  What is this thing for?
Can you post a photo of the "thing" you are talking about?  Could it be a electric vacuum generator(pump) rather than a air compressor?  Can you see a label or ID tag on it?

If it IS a vacuum pump you are looking at, the threads below may be helpful:

Vacuum pump under front

Vacuum pump, what is it?

During a quick Google search, I found a Airstream forum where they have some info on the Oshkosh VC22 chassis.  May be of some general interest to you?

Freightliner Chassis, Oshkosh, Clipper - Airstream Forums

The file below (VC-22RD chassis specs) also may be helpful, if not now, at some future date?

https://www.foreforums.com/index.php?action=media;sa=media;in=4961

Re: 1992 ORED Air Compressor Always On

Reply #2 –
Quote from: Paul GA –
1992 ORED, hydraulic brakes.  Front air compressor runs whenever the engine is on.  What is this thing for?
Diesel engines don't provide "engine vacuum,"  but that accessory vacuum pump provides vacuum for the automotive style heating and cooling for the cab.

Re: 1992 ORED Air Compressor Always On

Reply #3 –
So, sounds like it's Just for the AC, and has nothing to do with my brakes. I found a disconnected vac line in the dash going to the AC controls, haven't found the other end yet, so I'll probably just disconnect the pump for now and add it to the list for later. Thanks all.

Re: 1992 ORED Air Compressor Always On

Reply #4 –
There is a vacuum control for that pump that looks a little bit like a thermostat that has a vacuum line going to it and 2 wires. When it sees vacuum it opens the 12 volt circuit in the switch and stops the pump. It is round about 1 1/2 inch diameter about 1/2 inch high brass color held to the front wall with 2 screws.

Re: 1992 ORED Air Compressor Always On

Reply #5 –
Quote from: red tractor –
There is a vacuum control for that pump that looks a little bit like a thermostat that has a vacuum line going to it and 2 wires. When it sees vacuum it opens the 12 volt circuit in the switch and stops the pump. It is round about 1 1/2 inch diameter about 1/2 inch high brass color held to the front wall with 2 screws.
Vacuum switch is mentioned in the thread linked below, along with the vacuum reservoir.

95 u280 Grandvilla mystery pump

Re: 1992 ORED Air Compressor Always On

Reply #6 –
My vacuum pump operates the A/C controls as well as boost for the brakes.  There are no leaks, just issue with the cut-off switch, which I understand is almost impossible to find.  I see the Dorman vac pump for their diesel trucks mentioned as a replacement pump, but being that mine operates the brake boost as well, is this pump a good idea?

Re: 1992 ORED Air Compressor Always On

Reply #7 –
Are you sure it's boosting the brakes? Mine is very small and does not have the capacity for that.

Re: 1992 ORED Air Compressor Always On

Reply #8 –
Quote from: kgrover –
Are you sure it's boosting the brakes? Mine is very small and does not have the capacity for that.

I put in a switch on the vac pump cause the vacuum switch quit.  Once it pumps up and AC blows out the vents, and I shut it off, when I hit the brakes a few times the AC goes defrost.

Re: 1992 ORED Air Compressor Always On

Reply #9 –
Could be the air compressor for the Hadley air horns. Mine did just that when the compressor was failing. My horns still worked but after turning on the ignition the air compressor would run for way too long, then shut off, then start up and run again after a little while.
I replaced the Hadley Huffy air compressor with a Viair compressor, gauge, and a pressure switch. (the Viair came with its own gauge but I added another on the air line). Guess what? Now the system holds the set air pressure much longer than the 34 year old Hadley was holding. I kept the Hadley horn relay and the air tank in the system.

Re: 1992 ORED Air Compressor Always On

Reply #10 –
Quote from: nitehawk –
Could be the air compressor for the Hadley air horns. Mine did just that when the compressor was failing. My horns still worked but after turning on the ignition the air compressor would run for way too long, then shut off, then start up and run again after a little while.
I replaced the Hadley Huffy air compressor with a Viair compressor, gauge, and a pressure switch. (the Viair came with its own gauge but I added another on the air line). Guess what? Now the system holds the set air pressure much longer than the 34 year old Hadley was holding. I kept the Hadley horn relay and the air tank in the system.

Don't have air horns.
 

Re: 1992 ORED Air Compressor Always On

Reply #11 –
Please check, but very likely your brakes are hydraulic over hydraulic.  Nothing to do with vacuum.