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Old 12-07-2009, 09:07 AM   #1
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Warning light comes on

I just purchased a 2008 Monaco Diplomat with a Cummins 400hp motor and took it out for the first time this weekend to test it. When I was going up a long grade the warning light came on the dash. I pulled over and turned off the engine and looked up the in the manual what this meant. It said Out of range condition exists, have the motorhome serviced as soon as possible. I started the motor back up again and the light was out. I proceeded up the grade and it came on again. I pulled over turned off the motor let it sit for awhile then restarted the motor, no warning light. I decided to turnaround and go home. I went down the hill and home and the warning light did not come on. It seems to only come on when pulling a grade. Any ideas on what is causing the warning light to come on?

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Old 12-07-2009, 09:17 AM   #2
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First, seeing that this is your first post, welcome to iRV2. We're glad to have you join us.

Did you happen to retrieve and write down the OBD code designation (the code number)?


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Old 12-07-2009, 09:41 AM   #3
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Your engine is under warranty. A fault code should have been recorded. I'd recommend a trip to a Cummins dealer and have them check it out.
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Old 12-07-2009, 11:10 AM   #4
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I have a similar problem with the warning light and chime. Mine light and chime come on for about 1 second then turn off. Fortunately, I also saw that the right air pressure gage dropped quickly to zero then quickly back up to full pressure.

My service tech did a computer upgrade thinking that the problem would solve. My last trip ended yesterday. During the trip, the light and chime and pressure drop occurred about 10-12 times over the course of 2000 miles.

It occurs about twice, then won't happen again for hours. Then again, and so on. It's not the air pressure as the compressor could not possibly build the pressure back up to full from 0 in a second or less. More like a short or bad sender or something.

Anyone have this problem and find a solution?
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Old 12-07-2009, 12:48 PM   #5
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TM.. Yours just sounds like a loose connection... or ground

Dunes.. I'd go see your dealer asp
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Old 12-08-2009, 09:47 AM   #6
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TM, knowing your coach maker and year would help us to help you.

On Freightliner chassis, similar problems have been reported with the VDC, the interface box the drives the instrument displays. Generally, the instrument data is compiled on the the CAN buss, sent via common wires from the VDC across the wiring harness and split to the various displays via a "spider" harness. The data is common and each display watches for and displays its own data. So the problem could be a connection on your "right" (they should be designated front and rear) gauge or it could be a failure on the input side of the VDC. I had a problem with my speedometer dropping out much the same as your air gauge and it turned out to be the connection on one of the other chassis interface boxes. It took over a year and my getting the chassis wiring diagram (and all of the corrections to it) from Frieghtliner and specifically figuring out the data path myself. Since the sense air lines go directly to the VDC in my chassis, I'd doubt that there were any other components involved. As a side note, I did have a sense line hose failure a few years ago but that was a solid problem and I doubt you have that.

An easy trouble shooting trick might be to verify if it is the front or back brake system and then which color (mine are green and red) sense hose runs from it. Check the connection on the VDC for that hose.

If you have a Spartan or Roadmaster chassis, the whole setup may be different.
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Old 12-09-2009, 08:56 PM   #7
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I have a 2008 Endeavor that I got the same light when pulling big hills. I posted in the Cummings engine section, and got several good replies. I talked to a Cummings repair center and they told me it was most likely a bad sensor or loose connector, but couldn't tell until they read the code. Looks like it may be a common problem.

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Old 12-10-2009, 04:32 PM   #8
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Chasfm11---Very good point. I have a 2008 Gulf Stream Tour Master T40B on a Freightliner Chassis, 400 Cummins.

Neither gage is marked front or rear, etc. so I will probably have to disassemble the side dash and look at the colors. My guess would also be a loose wire or a short, but the problem is interesting. It happens on big bumps, and it happens when the road is smooth as glass. One would think that with either a bare spot shorting out or a loose connection, the problem would only occur when jolted.

Since I am slightly capable of doing some basic inspection, I'll start with the good ideas you all have responded with. As you all know, you can only fix what you can see and trouble shooting a problem that is NOT occurring is frustrating. I guess the positive side is that road test also means road trip.
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Old 12-10-2009, 04:52 PM   #9
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A couple of questions---How many miles does the coach have? Was the warning light accompanied by a loss of any power, other than what may be expected from the incline?

I have a 2007 Mandalay w/the 400hp Cummins with almost 13k miles. I just picked up my coach from a Freightliner Service facility for the same problem. My last trip was about a month ago and when I was climbing an incline there was a noticeable reduction in power and then the check engine light would come on. When I reached the top of the incline the light would go off. This happened a few times.

When in for service the fuel filters needed changing, the fuel/water separator was full of water, and the air filter needed changing (Apparently the filter gauges provided are not accurate). No other issues were identified. Hopefully this will take care of the problem.

Hope this helps.
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Old 12-11-2009, 08:18 AM   #10
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I had the low water warning coming on when going up steep inclines.The expansion tank was low.Maybe the wires are crossed.
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Old 12-14-2009, 04:37 PM   #11
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Hi glamisdunes,
Welcome to iRV2. I'll bet on Bob's answer. Newer coaches sometimes have to "burp" out air in the cooling system. Check the expansion tank. If the tank is metal and not see through, do not trust the sight glass. Take something rigid (coat hanger) and check the real level of the coolant.

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check enging light, warnig light

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