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Compressor replacement

My compressor is having issues.  It's been a bit noisy, but it has been working.  With this recent cold weather it seems to be seizing up. It runs fine at first, but the second time it comes on, it doesn't do anything and trips to over current warning on the watch dog. The breaker didn't trip, but the watch dog shut things down for over 50a of load. Any suggestions on options? It seems to be more cost effective to replace the existing compressor with a standard jobsite type compressor.  Or is that a bad idea?
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Compressor replacement

Reply #1 –
Several Forum members have replaced the OEM aux compressor with a different unit.  See threads linked below for some info:

12 Volt Compressor

What is the purpose of this HWH Tank Solenoid?

Inverter Replacement

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: Compressor replacement

Reply #2 –
Thanks Chuck. Are people replacing the 120v compressor with a 12v? Or do some coaches come with a 12v to start?
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Compressor replacement

Reply #3 –
Both.

Some have replaced the original 12V compressor with a bigger 12V high-capacity/high pressure model.  Some have used 120VAC powered shop type compressors to either supplement or totally replace the original 12V aux compressor.

High powered 12V compressors draw a lot of amps - will require new wiring from battery to compressor.

AC powered compressors may or may not run off inverter - depends on inverter size and air compressor motor LRA.

On my coach I have both type compressors.  The original 12V aux compressor still serves its function of coming on when required by the HWH auto leveling system.

I also have a Makita 120VAC shop compressor semi-permanently tied into my coach air system.  It sits on my pull-out joey bed and is connected into the coach air system by a rubber air hose and quick connect fitting.  The output from the Makita goes through a long length of copper tubing to cool the compressed air, then passes through a filter/dryer before entering the coach air system.  By manipulating valves, I can either use the Makita just to fill my tires with a retractable air hose, or I can direct the pressure to the wet tank and bring the whole air system up to 120psi.  This allows me to raise the coach for maintenance work without needing to start the engine.  The Makita does not run on inverter - I can only use it when on shore power or generator.

The Makita is the 3rd 120VAC air compressor I have mounted in our coach.  The first two died untimely deaths.  You can read about my earlier experiments in the thread linked below:

110V Aux Air Compressor Install

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: Compressor replacement

Reply #4 –
Something to note, both KGrover and I have coaches were the OEM compressor is 120VAC 3/4HP.
I rebuilt mine (kit # K263).  They are a really good quality compressors; GAST model 5HCD-010M500X.
The kits now are rather pricey at around $200.  I would disassembly and see if a cleaning will work.
That said they are kinda of loud.  I purchased a California Air Tools compressor only (to be quieter) but haven't installed it so I don't have an opinion if this is a good choice.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Compressor replacement

Reply #5 –
Quote from: JohnFitz –
Something to note, both KGrover and I have coaches where the OEM compressor is 120VAC 3/4HP.
Thanx, that explains the curious way kgrover was phrasing his questions.  I didn't realize they put AC powered compressors in some of the older model coaches.  Thanx also for the tech document.

Does the Gast compressor only work when on shore power or generator?  Is it only used for the HWH leveling system, or does it take the place of the engine driven air compressor found in other coaches (like mine)?

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: Compressor replacement

Reply #6 –
Quote from: kgrover –
Thanks Chuck. Are people replacing the 120v compressor with a 12v? Or do some coaches come with a 12v to start?

On my '91 U300 I replaced the 120V compressor with a 12V high capacity compressor. As Chuck stated I added high current wiring.

Portable air compressor
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: Compressor replacement

Reply #7 –
Quote from: Chuck & Jeannie –
Thanx, that explains the curious way kgrover was phrasing his questions.  I didn't realize they put AC powered compressors in some of the older model coaches.  Thanx also for the tech document.

Does the Gast compressor only work when on shore power or generator?  Is it only used for the HWH leveling system, or does it take the place of the engine driven air compressor found in other coaches (like mine)?


It runs off shore power and I'm assuming the generator.  I don't have a hwh automatic leveling system. I just have 3 levers in the floor next to the drivers seat to manually level the coach. It kicks on every few hours to air things back up when parked. I have some more air leaks to fix to eliminate that.
1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Compressor replacement

Reply #8 –
The OEM inverter is in the same location as the compressor so (unless removed) there should already be large 12 volt cables ready for a 12 volt compressor.
I have a leak too, but normally the compressor runs only about once per day.  I also have the compressor plugged into an appliance rated outlet timer so it doesn't run in the middle of the night and wake me up.  You have to find one that is digital with a internal battery so it remembers the time and program when the power it off.

To answer Chucks question, the compressor is tied into the main air system (with an isolator valve I'm sure).
The compressor could be used in a pinch if the main engine compressor failed - not sure if it could keep up the demand of the brakes and air bags though.  Could be used in a tow situation to keep the air bags up too.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Compressor replacement

Reply #10 –
Quote from: TGordon –
How about this: 110V, 120 psi, 56 dB


Amazon.com: CALIFORNIA AIR TOOLS CAT-1P1060SP GAL 56DB Air Compressor :...
That's what I was looking at,  that is less than the rebuild kit for the original.  It sounds like other people have used that or something similar with success.  I'm hoping that I can track down all the air leaks and only need it to kick on once in a while.
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1991 U300 Side Aisle 6V92 Silver #3897
2004 U320 40' #6246

Re: Compressor replacement

Reply #11 –

Turns out it was a bad check valve coming out of the air compressor. I ordered this from amazon and it fixed it right up. I also replaced the 30a breaker that someone swapped in for a 20a breaker for the compressor circuit. I'm not sure why the 30a breaker never tripped but the Watchdog tripped for over 50a. So I replaced that breaker to be safe. Pretty sure the watchdog kept my coach from burning down.

Control Devices-M2525-1WA Brass Ball Check Valve, 1/4" NPT Male: Industrial...

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