[Jerry]

There are a couple threads here titled Replace Aux Compressor. You either have an enormous air leak or your check valve or regulator are bad.

BA (Boater Al) has your vintage bus and will see this and advise I’m sure. He just went thru rebuilding his.

Later

bv

I just read your post again, your bed lift didn’t work? What about pocket doors?

On newer H’s the guage is on the top side of the generator in back. Can you pull your Generator out and see what the pressure is reading?

Where’s BA and Truk?

[Archived]

Tad,

You may have two compressor’s, one on the rear of the gen as Bernie pointed out and another for the Marathon house side. Marathon isolates their aux air from the Prevost aux system. There is a yellow knob in the steering bay that should be in the closed position. If you open that yellow valve, you then combine both Prevost aux air and the Marathon aux air.

The Marathon aux air feeds the seat, floor slide, foot rest in an H, pocket doors, bed lift and generator air bags. It has it’s own small air tank, on your vintage like Al’s, probably in behind the right passanger front fender and it has a drain somewhere as well. You may have a small 12 or 24 volt compressor that feeds those systems.

The Prevost aux air feeds the engine air bellows,suspension and possiblly a few other items such as the rear reverse spotlight. The Prevost aux compressor will likely be the one mounted on the generator and is 120v.

We can help you, but need to know which compressor is not shutting off. If you have no pocket door or bedlift air and one of the compressors is running constantly, that should be the clue where the problem is. If it’s the small 12 or 24 volt compressor, then you know you have a major leak on the Marathon side. It’s hard to explain all this via the forum.

E-mail me and I can send you my phone number if that will help.

Al?

[Archived]

I looked at a couple of 2000 Marathons before landing on # 591. How many AUX compressors do you have ?

If your AUX compressor is running continuous you should be able to hear air leaking. As mentioned above the worst is the main AUX compressor check valve, Check valve is available from Grainger and suggested to be replaced every 2 years, then the drivers seat, then passenger floor air slide, bed lift.

Start dropping items that use AUX air. Every one should have an air regulator with a black dial. This dial can adjust air pressure and can also be used to turn off air supply. The black dial pulls out to adjust then push back in to lock.

These supply valves are made by SMC and are available through Marathon or e-bay. I have a SMC supplier in KC if I can help that way. Most old SMC numbers are tagged on part, many have been superseded to other numbers.

The only one you need to be careful with is the generator mounted valve. That one must be replaced with a special one known as HEAT RELIEVING. As air temp increases in generator compartment air pressure increases. This special valve holds pressure at level you set..25 psi and will not increase.

Please, do not go to Home Depot buying a regulator which will not be heat relieving for generator room.

We can help you in many ways cure all your air leaks one at a time by isolating each system served.

Send me a private email to get your phone number to get started.

At one time our AUX Air was running once every 45 minutes. After repairs once every 5 days.

AL

[Joe]

Hi Al I emailed you I am south of Kansas City about 40 miles

[DON]

Good morning Peter, sent you a message about 10 minutes ago.

[Deleted User]

Hello All,

Thank you for your assistance. The compressor that was running continuously is the one in the generator bay, mounted on the inboard side of the generator. I do not know if there is another aux compressor. There is no problem driving the coach with this condition right?

[Mike]

Tad and I talked by phone and he found his leak in the engine compartment. The engine compressor can probably keep up Tad, but you want to check while sitting still and see how often the compressor has to cycle. You’ll hear the air dryer purge each time the compressor cycles, then watch your aux gauge to see how fast it drops. You don’t want to be on the road with a leak large enough to keep the engine compressor constantly cycling, it could get worse.

[Archived]

I want to reinforce what Tom points out. Any leaks need to be repaired. They never get better, and as they accumulate on a coach their collective leak rate can be large.

Our engine driven compressor has a 25% duty cycle. That means it has to not run 75% of the time. Since air is critical to the safe operation of the coach we all need to be aware of any issues affecting the system. The gauges will reveal the health of the system and if as you drive you can notice a loss of air pressure over a short period of time, such as one of the gauges (or more) going from 120 down to 100 and then cycling back up to 120 over a few minute period of time the leak rate is excessive.

At the very least do a standard brake check to make certain the leaks are not in the brake system. If the leaks are found when doing the test get the problem fixed immediately.

[Eric]

Today we went to Marathon and they found a leak on the rear camera door, the Aux Compressor check valve, and another one in the engine compartment (bus air side). I have only one aux compressor in the generator bay.

After the repair, the Marathon side worked great again. Until early evening when I heard the compressor running continuously again, the water closet pocket door was slow to operate, and only 10psi on the gauge in the generator bay. Lots of air coming from the black cyclinder at the top left side of the compressor.

Marathon installed a new pressure gauge, new compressor check valve, new regulator, and new generator bag regulator. Great service from Marathon. Maybe I just got a bad part?

[Richard]

Tad,

What did they tell you about the location and condition of the Marathon air tank we discussed?

[Archived]

If it was me, I would check the connections of every part that was replaced. Always check what was worked on or replaced last when a problem reappears. It might just be a loose connection on one of the parts they worked on.

[Bryan]

Hi Tom,

Marathon was not sure exactly where the aux air tank was, but they said it was not accessed through the front bumper. The tech thought it was behind the front fender. He showed me where I could drain both systems from the steering compartment. The tech had rusty aux air tank stories also.

Tad

[Richard]

Tell us how to drain the Marathon aux in the steering compartment please?

[Archived]

According to the tech, and unless I misunderstood him, both systems could be drained from the drain in the steering compartment. There are two drains in mine. I can’t remember which did both tanks, so I think I will drain both. I’ll let you know what I find.

[Archived]

Not doubting what you were told, but doubting the accuracy of that information. Why have two tanks if they share a common drain line? That means you have in essence one larger tank because they are not isolated from one another.