[rooster]

Can anyone tell me what this switch does, and where I might get one.  Mine is leaking.  It is located above the small air tank, located above and forward of the drive axle.  appears to be nylon body with two conductors leading to it.

[Chester Stone]

Photo out of focus.

[rooster]

Have determined it to be Bendix Low Pressure Switch 228750.  Not sure what it does but new one on the way.  Thanks  p

[Fulltiming]

Good catch. That switch activates the low air pressure warning light on the dash if the pressure drops below 60 psi. www.bendixvrc.com/itemDisplay.asp?documentID=4935

"The electrical contacts provided in both the LP-2™ and LP-3™ indicators remain closed by spring force until the air brake system pressure below the diaphragm is above the setting (force) of the low pressure indicator spring. The setting of the indicator and piece number is marked on a label on the valve body. If a label is not present, then the vehicle manual should be consulted for the proper setting. The nominal setting of the indicator is 60 psi; however, pressure settings may vary depending upon the vehicle.

OPERATION

To describe the operation, we shall assume that the low pressure indicator is set for 60 psi. When air pressure at the supply port and under the diaphragm is above 60 psi, the
electrical contacts remain open because the force exerted by air pressure underneath the diaphragm overcomes the force exerted by the spring above the diaphragm. When air pressure below the diaphragm drops below 60 psi, the spring exerts a force which is greater than the force exerted by the air pressure below the diaphragm. This causes the diaphragm (and the piston in the LP-3™ indicator) to move and allow the electrical contacts to close. This completes or closes the electrical circuit to the warning device, warning the driver of low air pressure in the system."

[Richard]

Not trying to throw a monkey wrench in this, and I agree that is what the switch is. It is just a weird place to mount the low air warning switch. They are usually on the brake tank or Newell has put them at the brake pedal valve.

Just wondering out loud if Newell appropriated a switch like that to 1. Provide a low air signal to the HWH system, 2 Turn on the 12V compressor, since it feeds that ping tank usually.

It would be interesting to short the leads to the switch and see if the low air light comes on.

[rooster]

Thanks Guys

I had that thought also.  I intend to bench test the old switch under pressure when the replacement gets here.  I will be sure it is normally closed and not normally open.   Thanks for responses.  It is surely in an awkward position, and difficult to trace let alone trying to get in there to replace it.  My Coach does not have a 12 volt compressor. Don't know if others of my vintage did. I am #174, 1988 model year. I know my 79 didn't.

[Fulltiming]

I believe they added the 12 volt compressor when they started adding the interior air operated doors and air operated toilets. My 1992 does not have the 12 volt compressor. I believe some 1994's had them. Not sure if there were any earlier than 1994.

Around the drive axle is the location of the pressure switch for the warning light on my 1992.

[77newell]

Mine is located in the rear where Rooster said his was.

[Richard]

Well Ok then! Sorry about the goose chase.

[rooster]

Thanks Michael. I think, and hope, that is what it is. I will have at it as soon as replacement arrives. I also have a waste dump valve on the curb side that has decided to drip. Need to rebuild that. Thetford 01447 Valve.