OTR bus air problem

[wrongagain]

problem solved

[Jon Wehrenberg]

Ed,

I have not dealt extensively with the OTR system, but if my system were responding but the clutch was not engaging my guess without the beneift of looking in the manual is that you might be low on freon. If system pressures are too low the compressor clutch will not engage. The first step would be to verify pressures.

If you have a burning desire to rule out an inop clutch, supply power to the clutch wire. If it engages you know the clutch is OK. I believe the AC system wiring diagram is on the cover of the box with the relays and CBs. You can access the service manual section covering your AC by going to the Prevost ?Car web site.

[wrongagain]

problem solved

[Petervs]

First put a voltmeter on the wire going to the clutch. If you have power there you know the control system is working or not. It will probably tell you the voltage also.

[Jon Wehrenberg]

Peter is correct. I should have been more detailed. You do not need to run anything to know if the clutch is working. Even if it 24V (I think it is) supplying it with 12V won't hurt anything.

Remove the belts and you will be able to rotate the clutch pulley without the engine running. Add power to the clutch wire and you should feel the pulley lock up. If it does and you want to continue the investgation just keep going backwards in the system to see why it is not engaging. All it is is a big electro magnet.

I would still suspect the freon is low. If it is, catch it while the system still has pressure and it can be refilled. The right way if it is a low freon issue is to vacuum the system, add about 300 PSI of nitrogen to make sure it is not leaking, and if it checks out, re-vacuum it and recharge the system.

Look behind the clutch. If it is a wet oily mess the odds are your compressor shaft seal is the culprit and it is a couple hour fix by a competent Carrier technician.