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Possible Coach Air System Problem

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Not sure if I have a problem or not with the compressed air system on my 2005 Monaco Diplomat. I put the RV in storage about 7 days ago and went over today to do a little work on the unit. The air gauge on the dash is reading about 50 psi. All the air is out of the air bags and the coach is sitting down.

When I start the coach the pressure comes right up no problem.

This is the second time I have noticed this happening. My question, is this normal or do I have a potential leak?

The coach is new to me so I'm not sure if this is normal or not.

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Is that rate of leakage acceptable per DOT and industry standards-- yes.

Is it possible with soap and water and small brush or "kiddie bubble" solution that you could find a small leak-- yes.

If you go under the coach to look for the problem, be sure to use safety stands.

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Thanks Brett - that was quick, you're right on top of this stuff! I'll keep an eye on the situation and see if the frequency increases.

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Yup, just got back from doing some work on the sailboat.

If you don't already have a copy, here is an air brake system check:

Air Brake System Pre-trip Check

1. Be on reasonably level ground. Block wheels so the coach can not move even with the parking brake off.

2. Start engine and run until full air pressure is reached. Listen for the dryer to purge (about 120 PSI).

3. Shut off the engine.

4. Release the parking brake by pushing in the yellow button (make sure you don't roll, and do NOT apply the brake pedal).

5. After the initial pressure drop, the system should not loose more than 2 PSI per minute.

6. Apply the brake pedal firmly (still with the parking brake OFF).

7. After the initial pressure drop, the system should not loose any more than 3 PSI per minute.

8. With the engine off, ignition on and parking brake off, rapidly pump the brake pedal to bleed down the air supply. During this stage you should watch for the warning light and buzzer at about 60 PSI and then the yellow button (parking brake) should pop out at about 30 PSI.

9. Restart the engine and build up air pressure again. While building up pressure, check how long it takes for pressure to go from 85 to 100 PSI at “cruising RPM”. It should be less than 45 seconds.

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Does the coach have jacks for leveling or is it an air bag leveling system? Our coach levels with air bags. Once the coach is leveled, the air bags will hold air fairly well while the brake side of the system bleeds air down to zero. If we have power, there is a small compressor which maintains the leveling system in active mode, keeping the coach level indefinitely. All the while the brake side of the system and thus the dash gauge are bleeding down to zero.

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No air leveling just hydraulic jacks. I just purchased the coach about a month ago and have not learned all it's little quirks. I'll keep a little closer eye on it and do as Brett suggested and put a little soap on a few of the fittings and see where that leads.

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With Brett's help, the culprit on my 2008 was the line going to the dash gauge. The gauge itself had to be replaced. So don't overlook the little areas when checking for bubbles.

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Why would the front air gauge fluctuate from 0 to 130 and low air warning light go off on diesel motorhome. It corrects itself after a couple of minutes and the gauge goes back to normal. It recurs again sometimes a minute later and sometimes an hour later.

Thanks, Thurmond Starling

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Why would the front air gauge fluctuate from 0 to 130 and low air warning light go off on diesel motorhome. It corrects itself after a couple of minutes and the gauge goes back to normal. It recurs again sometimes a minute later and sometimes an hour later.

Thanks, Thurmond Starling

What chassis? Your chassis maker fit your gauges and air pressure senders, so that is your first point of contact.

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The VDU module is causing the problem. Fleetwood / Freightliner generally located under the doghouse curb side. They have a cold solder connection issue.

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Returned from Freightliner with a new VDC board and $1,088 less money. Does anyone have a schematic

or instructions for repairing the old board? Be nice to have a spare as I kept the old board.

Thanks, Thurmond, 2001 Freightliner XC chasis

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Thurmond, Send me a PM with your contact information and I will send you what info. I have.

R.M.

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tstarling,

Welcome to the Forum.

PM=Personal Message. Click on ***** name and when his profile comes up click on send a message.

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Thurmond,

From your response it sound like you have a handle on the problem.

Thing is if you never need to use the repaired module it might make a good ebay item or item to list for sale at a Rally.

R.M.

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Ron,

Are you speaking of a wire or tubing? If it is a wire, Get some paste flux and a soldering iron. Apply a small amount of flux to the wire and heat with the soldering iron. The flux will start ot boil and the solder should liquify remove the heat. The solder should shine when it cools. Remove the flux residue and you should be good to go.

If it is tubing check as to the color of the filler metal. Pinkesh means Phos/Copper. If it is sliver looking then it is likely solder. If silver the process is the same as the wire but you will need a propane torch for your heat source. If it is Phos/Copper and the joint is copper to copper all you need is a high heat source, some sort of Oxy/Fuel would be good. (Note on Copper to Copper using Phos/Copper filler metal you do not need a flux) You may need some filler metal (Phos/Copper comes in 0, 2,3,5 or 15 percent silver). If you can get some 15% it should be good for repairing any of the other percents.

Any time you solder a wire connection it is best to remove the Flux Residue. The flux can hurt the wireing if it is an acid based flux, water is OK to remove the residue.

Hope this helps,

Herman

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I just went to take our Monoco Windsor out of winter stotage and it wont build air pressure. Only 10 or 12 lbs. can hear air by left rear wheels. Could this be same problem? Or stuck relay maybe?

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Blownaway,

Welcome to the FMCA Forum.

The good news is that you have an air leak large enough to easily locate. There are a number of components in your air system that can leak-- could be something as simple as an air hose that a mouse chewed through.

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I have a 2008 Excursion 40' diesel.

After parking and leveling I release my suspension bar to lower the coach's air bag system and the coach lowers. Good, but if I need to use air to fill my tires, after starting the engine the air bags fill up but do not lower the coach after I shut off the engine off? I release the suspension bar but no air is escaping like when I first park the coach.

Thanks for any feedback.

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