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Rear tank low air pressure warning

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I have a 2009 HR Ambassador 41 SKQ. Last winter while traveling to AZ., I got a Rear Tank Low Air warning and buzzer. We stopped in Amarilo, TX. and the repairman replaced the sending unit, located on the rear tank, and equalizer valve. Did not help. Since both tanks were holding 123 psi, we guessed not an air problem. After arriving in Mesa, I had a mobile repairman come by, and of course, everything worked perfectly. We assumed it was moisture in line partially frozen. So, I drained both tanks and replaced the moisture filter. Heading home, after about 50 miles, message and buzzer return. When pressure was above 65 psi buzzer and message would stop, then I could see the digital readout on message center. The front tank held at proper level, but rear would jump and fall so fast you couldn't read the numbers. Most of the way home it stayed above 65 psi, so no buzzer. After getting home I took it to a shop and was told I needed to replace the pressure sensor located in the generator compartment, which I did. Did not fix problem. I switched the wiring from the front to the rear sensor, just to see if the new sensor was bad, but the guage stayed the same, front ok, rear tank warning and buzzer. So, the next thought was the guage is bad. Replaces guage, did not help. I also replaced the park break pressure switch. I'm at a loss of what to do next, and ideas?

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You switched sensor wires between front and rear and still indicated bad rear pressure?  Or did the problem stay with the rear sensor?

If it's jumping around multiple times / sec I'd say wiring somewhere . . . maybe a ground wire (if it's a ground reference). 

I can't offer specific help, just throwing up some basic questions.


- bob

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If you suspect a grounding problem go to your chassis or house batteries, depending on the component, and first check for resistance between the negative post of the battery and a clean metal spot on the chassis. Use firm pressure on the test probes and a decent quality multimeter. Your reading should be zero which verifies that the chassis grounding path is good. If not you should remedy that problem before proceeding. Some components are more sensitive to grounding problems than others and important components usually have a ground wire going to a grounded stud or pad. Then check the grounded housing of your problem device to the chassis as before. Must read zero ohms again.

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