Air Pressure low

[sam-tip]

I am having problems with air pressure. It is a 2008 Winnebago Tour with maxium chassis. Sometimes when I start the RV the air pressure does not come up to normal pressure. It is like the air pump is turned off. I pulled the air relief valve and the air pump is just pumping a little bit. If I run the engine at 2000 rpm I can get air pressure up to 65 - 70 psi. This will turn off the low air alarm. Then once I get moving after a 1/4 mile the air pressure will come up to 115 psi and be fine for the entire day. The RV has done this to me four times now. Many times it will work just fine. Start the RV and the air pressure come up to normal. But it is becoming more frequent. I have replaced the desiccant in the air drier. It will hold air pressure for about a week sitting. I have changed the pressure relief valve to 200 psi from 175 psi. At 175 it would pop off and release air pressure. But with the 200 psi value it does not. Just getting surges of air.

My guess is the air governor. Is the governor part of the air pump?

[J Walker]

The dash re-gauge may be wrong. Mine was and I have heard of others that have been. When the gauge reads low pull the relief valve and see if there really is pressure. If your gauge is reading low is is probably the Dash Controller computer. There is a fix for the computer if it is the problem.

[sam-tip]

I believe dash gauge is reading ok. There is not enough air to fill the air bags until it starts building enough air pressure. Very bumpy ride for a little bit.

You can also tell from the parking brake button. The air pressure is low. It doesn’t make the loud popping noise when I set the parking brake.

[Wayne M]

Sam-tip,
It sounds like you need to make a trip to a Freightliner service center. You have a two year warranty on chassis parts and labor. Driving without your airbags full is not a good idea, and also the possibility of your brakes locking if you loose pressure.

Good Luck.

[sam-tip]

I did not know of a two year warranty from Freightliner. I thought I only had a seven month warranty from Winnebago. The unit was a factory demo with 7000 miles when I purchased the unit on March 7th 2009. Build date was Jan 2007.

[Vegasdan]

Two year chassis warranty comes with Freightliner.

[Wayne M]

Call the Gafney Freightliner plant and speak to a technician. They will ask for either the VIN or Serial Number. They will be able to tell you when your warranty runs out. The dealer should have registered it for you, but the VIN/Serial should be verifiable by Gafney.

Good luck.

[sam-tip]

I will give them a call.
I got thinking about this the other day when I put the RV back in the barn and the air pressure would not rise again. When I turned the key off the electronic light bar control unit (LBCU) did not turn off. It stayed on and lighted. Then I could not start the engine. I would try to start the engine and it would not activate the starter. Noticing the light bar control unit was still on I turn the battery disconnect at the chassis batteries and disconnected the house batteries with the switch near the front door. I left the batteries off for a minute and reconnect the batteries. Then everything worked fine. The air pressure worked and the engine would start.
This got me thinking. The times the air pressure would not work is after we camped without shore power (overnight stop at Walmart). We would use the generator and the inverter to run everything. We normally only use the generator for about 2 – 3 hours twice a day to charge up the batteries. We mostly use the inverter. Could the generator or inverter be causing problems with the chassis cpu? I have ran the house batteries down to 9 volts because I forgot the refrigerator was on auto not LP. With the house batteries low there is not enough power to start the generator. I had to start the main engine to get enough power to start the generator.

[sam-tip]

Think I got the air generator working. I extra cleaned all the battery terminals and the air generator has not failed yet. The terminals were not bad. Voltage went from 13.4 to 13.7 at the front display.

Thanks

[MaverickBBD]

Repeat after me: 1 800 FTL HELP. They have tecs on call 24/7 365 days a year. If the one taking the calls is busy (assisting someone else) they have 100% on their call backs.

[azloafer]

Quote:

Originally Posted by sam-tip I believe dash gauge is reading ok. There is not enough air to fill the air bags until it starts building enough air pressure. Very bumpy ride for a little bit. You can also tell from the parking brake button. The air pressure is low. It doesn’t make the loud popping noise when I set the parking brake.

Our coach takes longer to air up ever since we had the SS motion control units added. I like the MCU's, but now I have to wait longer before driving; sometimes 5 to 10 minutes. Joe

[sam-tip]

Follow up. Took the bus in to Frieghtliner of Des Moines. They rebuild the air pump and installed a new fuel tank sending unit. No charge. Only took 7 days.

[azloafer]

Quote:

Originally Posted by azloafer Our coach takes longer to air up ever since we had the SS motion control units added. I like the MCU's, but now I have to wait longer before driving; sometimes 5 to 10 minutes. Joe

Update from Freightliner:
The jacks are tied in with the air dump system because the jacks will not have to travel as far to level the RV and this gives the jacks more length they can level. If the air was in the bags the jacks would not give you as much movement. Most all manufacturers have it set up this way. It does take a few minutes for the bags to air up, especially with motion control units added. You can try to fast idle the RV to see if that helps. Some times increasing the rpm's at idle will allow the compressor to run a little faster. Also look at your air gauge. If it is not moving Pump the brake and allow the compressor to come on. This will get the compressor going allowing the bags to fill up. It will take longer when the bags are empty compared to if you just stop and do not operate them.

[EasyDoesIt]

Glad to hear the solution. I had a problem with my Freightliner Chassis leaking down overnight. Freightliner service found a leak. Now pressure stays up overnight.