[Tegra1027]

I am helping a friend that is in a sticky situation. I am mechanically inclined, but not a mechanic. I'm hoping someone can guide me. 

This is a 96, with no slides. When I first worked on this coach almost 2 years ago, I couldn't get the rear end to lift up enough to safely drive around. It did once or twice and I had to manually lift it on the HWH pad. No Other issues with the air system. 

Now, I have brake pressure. I hear it release at 120lbs. But I have no air supply pressure and I can't get the bus to lift up. I don't hear any leaks. I tried letting the bus run for an hour as well as trying shop air. I'll include a few pictures of current ride height and the gauge that I'm reading. 

I don't know Newells. I'm begging for your help. Thank you.

[Jack Houpe]

I would suggest to get a cup of coffee and watch all these videos or have the owner of the coach watch them. There are 3 compressors aboard your coach, the main engine compressor the 120vac compressor and a 12v compressor. You say that you hear the air dryer sound off at 120 psi but there is no indication of PSI on the dash? Check your PPV valve.

https://www.youtube.com/watch?v=7rnRcyW96m4

[Tegra1027]

Thank you for your reply. On this bus there are two air gauges. One for the brakes and one that says Air supply. The gauge for the brakes reads 120 lb, but the air supply gauge reads zero.

I've done a little bit of research in the very minimal time that I have. I understand there are three air compressors on board. I have not been able to supply 110 volts to the bus for that air compressor to work. And I'm not even sure where the 12 volt air compressor is to see if it's working. But from what I understand, it really doesn't matter. The engine compressor should supply air for all air systems that require the bus to move I.e the brakes and the airbags. Am I correct with that?

The PPV valve makes sense. Any idea where I might find it? I know all the buses are built differently, but I'm hoping that they're somewhat in the similar area to one another. What would I check for exactly?

[ccjohnson]

The PPV should be underneath the coach inside the frame rails at approximately where the rear wheels are. Bad news is that you will have to raise coach to get to it. When mine went bad, the mechanic that came to the house rigged up at fitting to apply air to the discharge line on the 120V compressor. This supplied air to the "Supply " side of the air system. We were able to raise the coach with this air supply. Be sure to crib the coach properly before going underneath it. Most truck roadside mechanics should be able to fix this for you. Alsoon mine it took a day to get parts in.

[Tegra1027]

That makes sense. Is there any way to check to see if it's actually bad or should I just replace it?

If I need to replace it, is there anywhere to find out what part number I need?

Just for sake of understanding, the engine compressor should supply air to the reservoir tank for the airbags. But because it's not, using the 120 air compressor should do the same and it's just another avenue that would bi pass the PPV valve and possibly other components that may be an issue here?

[Richard]

Ok, in front of the rear axle, center of the coach, you will find a bulkhead wall. The PPV is mounted on that wall. It’s a generic PPV, take a picture of it, and go to a truck supply place.

You will need long arms to work in there, it’s not easy access.

And please support the coach while under there, no need to get injured or worse.

It will look something like this. https://b2bendix.com/US/en/USD/Products/...14-012-001

You may be able to rap it with a percussive instrument and get it to function, but that is not a long term fix.

If you must move the coach, then hook shop air to the port in the rear engine bay, that will feed air into the supply side.

[Jack Houpe]

That makes sense. Is there any way to check to see if it's actually bad or should I just replace it?

If I need to replace it, is there anywhere to find out what part number I need?

Just for sake of understanding, the engine compressor should supply air to the reservoir tank for the airbags. But because it's not, using the 120 air compressor should do the same and it's just another avenue that would bi pass the PPV valve and possibly other components that may be an issue here?

From my understanding if you can get the 120v compressor running it should raise the coach with the key on and in one of the modes like travel. The PPV valve should pass air in both directions IF there is no problem down stream of it. Suppling air pressure from the 120v compressor may dislodge it but if its 27 years old and stuck now I would not trust it even if it did free up. I can't tell you the part number but you could call Newell and perhaps they could tell you. Jack stands are needed to do this safely or cribbing. You will need to determine if you have a major air leak or if the PPV valve is stuck, I would not bypass it I'd just take it out and replace it. If you get the 120v compressor going and the coach raises and holds pressure its the PPV valve for sure. The little 12v compressor is mainly to flush the air toilet or open and close air doors. I am not experienced in this system yet but have watched Richards videos and he explains it well.

[Tegra1027]

Ok, in front of the rear axle, center of the coach, you will find a bulkhead wall. The PPV is mounted on that wall. It’s a generic PPV, take a picture of it, and go to a truck supply place.

You will need long arms to work in there, it’s not easy access.

And please support the coach while under there, no need to get injured or worse.

It will look something like this. https://b2bendix.com/US/en/USD/Products/...14-012-001

You may be able to rap it with a percussive instrument and get it to function, but that is not a long term fix.

If you must move the coach, then hook shop air to the port in the rear engine bay, that will feed air into the supply side.


I did supply shop air, it did not raise the coach at all. I'll try freeing it up. 

[Richard]

Interesting that shop air did not work, welcome to no two Newells are exactly alike.

Did the supply gauge on the dash register pressure when shop air was applied?

[Tegra1027]

Interesting that shop air did not work, welcome to no two Newells are exactly alike.

Did the supply gauge on the dash register pressure when shop air was applied?

It did not. Im going to try to move the coach to my shop again and plug it in. Ill have 50 amp available on Thursday. If I can do that and get the 110V compressor working, then maybe that will work. At least that way it would confirm the PPV Valve is bad. From what Ive been told anyway. 

Being that the coach has been sitting, I cant help but wonder if a check valve has gotten rusty and is now stuck.