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Coach Air System

May 30, 2014, 04:51:01 pm

I have a few questions about the operation of the coach air system. After the coach is parked for a few days, it takes about ten minutes for the air gauges to show more than 100 PSI. After reaching that amount, the coach will show Travel Mode and while traveling the air gauges will show between 100 and 120 PSI. Also, after being parked, and turning on the key to start the engine, the air pressure gauges show 0 PSI. I am not sure if this is normal or not. I am not sure if this is related but while parked and leveled, the coach stays level and the air compressor hardly ever comes on to re-level, even after four or five days leveled. I am quite sure something is wrong for the air system to take so long to reach Travel Mode, but I have no idea what is or could be wrong. Thanks for any help.

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Re: Coach Air System

Reply #1 – May 30, 2014, 05:01:03 pm

 I think travel mode shows around 80lbs and if your gauge shows 0 when you turn switch on to start again that is either a solenoid or problem associated with gauge or sender-I would think or your govenor is faulty and not allowing the air to build up. 0 to 100 at start should be only take a minute or less.
JohnH

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Re: Coach Air System

Reply #2 – May 31, 2014, 10:23:04 am

The description from LTG all sounds normal to me. You could fix a few leaks in fittings and check valves to keep the pressure in the main system from falling while the engine is not running. Ours used to fall to zero in 12-24 hours. It takes a few days to fall to zero now.

You can speed up the process of reaching 100 psi by engaging the fast idle control on the cruise control. We are comfortable moving our coach after the pressure reaches 90 psi. The pressure rises to 90 psi much faster with the idle speed at about 700-900 rpm than it does at the normal idle of about 550 rpm.

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Re: Coach Air System

Reply #3 – May 31, 2014, 10:26:37 am

I thought that anything under 4 minutes to build from zero pressure to operating pressure was considered acceptable.

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Re: Coach Air System

Reply #4 – May 31, 2014, 11:45:18 am

On my 2003, if the tanks are near zero at startup, it takes quite a few minutes to reach 100 psi.  Don't know exact number, but is certainly more than 5.  May even be 10.  Even from my normal sitting value of 65 psi it takes quite a few minutes to reach full pressure. 

While driving, my pressure varies between the compressor setpoints (something like 100-120 psi).

How much air remains in the tanks during shutdown depends on how much you use the step cover or any other air operated systems and system leaks.  If you do not use your step cover very much and your pressure drops to zero, then you have leaks.  After sitting for a short time, my tanks will bleed down to about 65 psi and stay at that pressure for weeks.  Others have reported that their tanks stay at 100 psi, or so.  I assume this difference is due to the type of pressure regulator on the HWH leveling system.  Mine is a "relieving" regulator.  Then again, there may be a problem I have yet to identify.

The HWH compressor does not maintain pressure in the main air tanks unless the "Air Tank" switch by the driver's seat is turned on.  While parked, the HWH compressor only keeps the slide-out seal tank pressurized (mine comes on about once or twice a day for about 2 minutes).  The compressor may also come on if you adjust the coach level.  The leveling system turns on the compressor anytime a "raise" function is initiated.

There are many places where you can have leaks.  Chasing them down can become a never-ending task, as many of us know.

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Re: Coach Air System

Reply #5 – May 31, 2014, 11:47:36 am

Just a suggestion-- one that is better for the engine and also for speed of air fill:

When starting, after engine runs at low RPM for a minute, use the cruise control to bump up to high idle for faster engine warm up and air fill.  1000-1100 RPM is good.

Brett

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