Skip to main content ↑ ↓
Topic: 1992 ORED Air Compressor Always On (Read 553 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?
1992 Foretravel 36' Grand Villa ORED - VC22RD Chassis - 8.3 Cummins

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

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

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.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

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.
1992 Foretravel 36' Grand Villa ORED - VC22RD Chassis - 8.3 Cummins

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.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

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

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

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?
1992 Foretravel 36' Grand Villa ORED - VC22RD Chassis - 8.3 Cummins

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.
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

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.
1992 Foretravel 36' Grand Villa ORED - VC22RD Chassis - 8.3 Cummins

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.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

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.
1992 Foretravel 36' Grand Villa ORED - VC22RD Chassis - 8.3 Cummins

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.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020