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Another OTR AC question
I have been going through the bus systems one by one since I bought it in August. Making good progress. Now it is time to take a hard look at the OTR system. When I bought it the system was charged with 20lbs of 134a freon and the system seemed to work on the way home (not extremely cold but clearly cooling). When I tried it recently I did not get any cooling.
With the engine at high idle, the compressor is running and the condensor is making a rythmic buzzing noise. The condenser fans are not on and I can’t see any freon in the accumulator. I did not run it for 20 min as the service manual suggests for fear of damaging the compressor (I can’t see any oil in the sightglass). Oh, and the humidity indicator shows the system is “wet”.
Someone was mentioning LED indicator lights to help with system diagnosis – where would those be?
My guess at the next steps are
- Evacuate the system and check for leaks
- Remove moisture, replace drier
- Recharge
Are those the right next steps? What other troubleshooting steps should I perform?
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5 Replies
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If the system has sufficient pressure the compressor will engage, if the system pressure drops such as in a low freon situation the compressor will not run. When the compressor runs the condenser fan(s) should also run.
On two coaches I have had the circuit breaker for the condenser fan fail open so before I do much else, if the fan does not run with the compressor I look immediately at the CB to make sure it has not opened. On both instances I could reset it, and within a short period of time it would trip again.
I wouldn’t even mention that CB but your comment about the condneser fan not working got my attention.
Yes if electrically the system is OK then sticking the gauges on and seeing what is happening is the next step. The gauge readings will tell you what is needed next.
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If your fan is not running another thing to check is the brushes on the motor (4) each motor.
Due to dampness and graphite dust they are known to stick in their track and not make contact with the armature.
Note: if the spring pushing on the brush is at the height of the track/channel the brush slides in then the brushes need replacing.
The fan assembly must be removed from the coach to change the brushes.
If anyone is interested I will post a how to with pictures. The job is straight forward and any mechanically inclined person can perform the procedure. Allow one day in good sun light outside. Be prepared to offer ear plugs for all onlookers due to cussing.
JIM
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27#? Also does your dash lite say low HI or not lite up at all? Will call Sean he just had problem with his H and thought it was condensor fan but was relay instead. His lite read Hi. His freon charge was full charge. Bob
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Talked to Sean: They found a bad relay in the box Above the Batteries in the Engine compartment. It was passing partial power to the condensor motor. If you condensor motor is dead I have a low hrs replacement. Trade or cheap. Bob
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I checked the breakers in the condensor bay. Both are on. The red/green LEDs on the dash are out. In fact I have never seen them on. What do they / are they supposed to indicate?
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