Low air alarm in 2000 Monaco Diplomat

Sorry, Air systems should be OVER 110 PSI. The cut off for a Air System alarm is the 70 to 80 PSI. So, the system is accurate. Your problem is inadequate air pressure in the tanks. OR the air PSI gauges are wrong and your air is over the 110. Regardless, if you show 80, that is your problem. I have never heard of a Air alarm going OFF when the key is OFF. Makes no sense as when parked and you exhaust the air system, the alarm would go off if wired for HOT all the time. Doug

If air system maxes out at 80 PSI, most likely "suspect" is the AIR GOVERNOR.

Not expensive or difficult to replace.

jackie wrote:

JRscooby wrote:
What does the gauge say?
Power to buzzer should be switched by main switch

The gage reads what it always has, between 60 and 80.

Everything works great, brakes, air ba suspension, but the darned alarm will not turn of, whether the key is on or off.

If I knew the wire that fed it electricity, I would disconnect it. Right now, I can’t even find the alarm, and I have the dash taken apart.

Sounds to me you have more than 1 issue.
First, if your system maxes out at 80 and has for a while you have a bad compressor or more likely leaks. If you have been driving like that you should be shamed.
If the buzzer is on with the "ignition" switch off, you have power getting to it from someplace it shouldn't.

The low pressure warning SHOULD come on before pressure is lowered to 60 PSI.

If you start the engine and build PSI back to cut-out PSI (assuming 110+ PSI) is the alarm still active?


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.

JRscooby wrote:
What does the gauge say?
Power to buzzer should be switched by main switch

The gage reads what it always has, between 60 and 80.

Everything works great, brakes, air ba suspension, but the darned alarm will not turn of, whether the key is on or off.

If I knew the wire that fed it electricity, I would disconnect it. Right now, I can’t even find the alarm, and I have the dash taken apart.

What does the gauge say?
Power to buzzer should be switched by main switch

After 20 years the Lo air pressure sensor is either bad or wires loose. Doug

Wonder if more than just low air could be triggering the alarm?