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Old 11-01-2006, 11:47 AM   #1
Greg Reed
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Default Schematic's for air suspension system

I was looking for a schematic of the coach's overall air systems, and especially the air suspension system. I have a '83 (#007), and at that time schematic's were not part of the manual.

Anyone have a mid to late '80's schematic? I have started to trace out leaks, or other potential problems relative to why the air pressure takes so long to make 90psi, and drivers side tends to tilt down.

I note that the 120 volt air compressor (not sure, but looks OEM) is quick bring the system air to 50/60 psi, but appears to have a pressure switch cut out to keep it from raising the pressure higher. Still can not find the switch.

It would be a lot easier to mark-up a schematic, versus drawing from outside and under the coach.

thanks,

Greg
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Old 11-01-2006, 03:12 PM   #2
fulltiming
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I have not seen a schematic for the air system and would be doubtful that they exist. The 120 volt pump on my coach turns on at 72 psi and shuts off about 95 psi. A worn pump will build up pressure initially but as the pressure increases it will take more and more time to bring the pressure up the last 10 psi or so. These compressors will overheat if they have to run for lengthly period and may shut off on a thermal overload. I had mine replaced at the factory recently because it would come on at 72 psi, pump up to about 80 psi in a 3-5 minutes, then run for 30 minutes or more trying to get the last 10-15 psi into the tank. At times it would shut down before reaching the 92-95 psi range due to overheating. The new pump takes about 3-1/2 minutes to bring the pressure up to 95 psi from 72 psi.

If you have the drivers side up after leveling then listing after a short time period, you likely have a slow leak in the right rear air bags or the air lines or fittings running from the solenoids in the rear to air bags.

My 1992 has an HWH air leveling system and the remainder of my comments are based on the operation of that system.

My coach has 12 solenoids in the right rear engine compartment for the air system and 6 more solenoids for the air system in the front left of the coach which you have to access from underneath. I had the solenoid that dumps the right rear sticking so I had all 18 replaced as a precautionary/routine maintenance measure as it appeared that they were all the original 1992 solenoids. They are about $87 each for the parts.

If the coach never levels properly when in LEVEL mode, there is a level sensor, which on my coach is in the drivers side compartment directly behind the mid-entry door hanging from the top of the bay on the center line of the coach. That sensor is adjustable if the coach thinks it is level when it is not. That part of the circuit ONLY works when you have the leveling control in the LEVEL mode rather than the TRAVEL mode. Leveling in the Travel Mode is controlled valves connected by rods to the axle at the center of the front axle, and on each side of the drive axle.

The air bags require a LARGE volume of air to inflate. Trying to raise even one corner of the coach very much typically requires the engine running on Fast Idle to produce enough air.
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Old 11-01-2006, 03:59 PM   #3
Greg Reed
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My inital concern was the long time to bring the unit up to 60 psi (more then 10 minutes), using the engine mounted compressor. Once it hit 60 psi I could use the accelerator to increase engine speed, and then bring the total air pressure up to 90 psi range and ready to travel if all other issues were OK.

I have had the primary (engine mounted) compressed tested, and it is well within spec, so started to look for leaks in the system. So far found a few loose tubing fittings.

I also thought about using the 120V compressor to provide a boost in the air system, to help look for leaks, and when plugged into land power before starting the engine. Each time (only tried a few) the unit would run for a few minutes, and then shutdown shutdown at 60 psi. I can not find any indication of it being a thermal overload. shutdown.

The '83 also has the similar setup of solenoids, and locations, but I do not have any documents that define the system. I will start looking for the level sensors.

thanks for the input,

Greg
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Old 11-01-2006, 05:29 PM   #4
fulltiming
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How long does it take for the pressure to drop in your system? I would think that if it takes 10+ minutes to get the pressure up to 60 psi with the engine compressor you must have leaked out most of the air in your system. My engine mounted compressor comes on at about 90 psi and will pump up to 125 psi before it shuts off. My 120 volt kicks in and out at lower pressures than my engine mounted compressor.

It takes a minimum of 60 psi for the air slide on the generator to operate. The complication of the air system on the Newell does offer multiple sources for leaks. The more air operated equipment you have the more complex the plumbing. Many Newells have air bags, air slide for the generator, air slide for the entertainment center/freezer in the bay, air slide for the stairwell cover, air operated dump valve on the passengers side, and on the recent models air operated doors giving many chances for leaks.

I don't think I have ever let my system drop below about 70 psi since I live in my Newell and keep the 120 volt compressor switched on all the time. However, when I start the engine, it does take a couple of minutes to bring the pressure from 80 psi or so up to 125 psi even if the air bags are properly inflated. When the air bags start inflating it takes a long time it the engine isn't on fast idle and several minutes even if it is.

With air brakes, neither of the compressors should be cutting off at 60 psi since 60 psi (or 1/2 of the compressor governor cutoff pressure on older vehicles) is the pressure that the low air pressure warning system should come on. Air brakes use a lot of air and if you are truly starting at 60 psi you have little safety factor for the air brakes. Start the engine and as the pressure starts to increase, see if you hear air escaping, particularly from the front of the coach. You may have a dump valve or a solenoid sticking in the open position. That will really slow down the tank pressure buildup.
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Old 10-29-2007, 07:12 PM   #5
Richard and Rhonda
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Hi Greg,

Looks like I am about a year behind you in figuring out the air system. You probably have if figured out and fixed by now. However, what you are describing sounds like a worn out 120Volt Air Pump. If yours is manufactured by GAST as mine is, you can buy a rebuild kit for the pump for a lot less than replacing it.

Richard
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