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Old 11-06-2016, 03:16 PM   #1
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Front Air Bags issue

I have a 2002 HR Imperial, been trying to find the problem with it taking at least an hour to fill front air bags. Replaced Height Control Valve and had filter replaced on Air Dryer, did not help. While I was starting up the other day I had the Generator pulled out and I noticed quite loud air sound coming from a small aluminum box on the firewall above the generator, in the middle of all of the bundled cables. Does anyone know what is in the small box or what it is used for. I wondered if there is a valve or something in it that could be not working properly? I also attached a picture of the small box and bundled cables.
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Old 11-06-2016, 03:29 PM   #2
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It might be a venturi powered vacuum pump. Air is blown across a small opening, creating vacuum to power your HVAC controls. If you don't have an electric vacuum pump, the chances increase that's what it is.

Do your dash air gauges take an hour to build up pressure also?
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Old 11-06-2016, 03:40 PM   #3
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Dash gauges go up like they are supposed to, also the rear air bags build up like they are supposed to also. It just takes at least an hour for the front bags to fill up. I thought that maybe I was losing air from what is inside the small aluminum box. Also when I shut the engine off the air sound stops. After the bags are filled up they stay up for at least 3 or 4 days, I was told if that is so I probably did not have a leak, just something to do with filling the front air bags.
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Old 11-06-2016, 04:50 PM   #4
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So if the compressor builds pressure as it should, it's either a bad ride height valve or some other blockage in the system. As long as you're sure the frame won't drop so far as to squeeze you, you could disconnect one end of the ride height valve and push and pull the lever to see if the bags build up faster when the valve is exercised.
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Old 11-06-2016, 06:13 PM   #5
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It's time to get the unit up and secure on some blocks under the front wheels... and get a spray bottle of soap and water and look for a leak... and than check for a pinched or kinked air like...

The air drier filters all air from the compressor to the air tanks.... if the air tank gauges are up to normal than you have nothing wrong with the compressor or drier... all service air... for the brakes, air bags, leveling or any other needs of compressed air come from the service tanks behind the drier...

You problem has to be a slow leak... and you'd notice this as the compressor would cycle often... remember that when the compressor cycles so does the drier... the air drier is triggered from the compressor going to idle and shutting down.... the compressor is a designed to run no more than about 15-20% of the time... and often if you run down the road and don't use the brakes... you might go hours without the compressor running....

SO your looking for a plugged line, kinked line, leak, or valve that isn't opening correctly... on most leveling systems... air passes through a open solenoid, to a leveling valve to the air bags.... when you lower the system... the solenoid closes and bleeds the air down, on the air bag side of the solenoid... of course it a little more complicated than this if there are automatic controls... but this is a basic overview...

Hope this helps you better understand the system.. One last thought.... if your tanks bleed down overnight... you have a leak and need to find it... and if you've never drained the air tanks than you need to consider that moisture from the tanks has passed through all the valving on the vehicle...
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Old 11-06-2016, 07:02 PM   #6
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You might be hearing air discharging from the dump valve. The valve is controlled electronically when you dump the air bags but there may be dirt in the valve not letting it completely seal off explaining why you can't get the front air bags to inflate.
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Old 11-07-2016, 08:36 AM   #7
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I have replaced the Ride Height Control Valve, it is working properly. I have drained the air in the coach many times, everything there seems to be working properly. It takes days to drain down if I do not drain it manually. Could a small leak cause it to just take it longer to air up, as in about an hour, or more likely a valve issue? Once it is up it stays up for a long time. I could be mistaken but Tech Help told me that it is normal for the air to drain down in 3 or 4 days. I did purchase a Pressure Protection Valve, thinking that could also be the problem. Thanks everyone for the help.
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Old 11-07-2016, 09:24 AM   #8
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I don't see a leak because of your 3-4 day bread down rate. I see a kinked or blocked line. Your rears build up right.
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Old 11-07-2016, 09:47 AM   #9
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I'm with jacwjames........ on my '99 Windsor, the dump valves for the front bags are located just to the right and above the generator. It sure sounds like yours are not closing properly.

My front valve actually has a quarter turn shut off valve on the discharge side. Not sure what that is for as the rear valves do not have anything like that. I can actually close the front cut-off valve and then hit my air dump switch and only the rear bags would deflate, not sure why anyone would ever want to do that.




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Old 11-07-2016, 07:42 PM   #10
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If you have more than one air tank you could trace the air from the bag to the tank and then schec just like you would do on an electric problem. Check air into the tank, air out of the tank and any connections between all the while checking for a crimped like as has been suggested. A small flake of rust can stop up a lot of air flow.
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