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winfarnsworth

Dash A/C Cutting Out

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The dash A/C in my 2011 Monaco Diplomat cuts in and out. It totally failed about 9 months following purchase. Factory service determined the fuse was blown, and they replaced the fuse with a 15 amp relay. The A/C now runs great for a while, then cuts out (warm air). After 15 or 20 minutes, it kicks back in and cools. The ambient temp seems to be a factor in the frequency of the problem. I'm reluctant to increase the size of the relay in fear of overheating wiring. Can it be it be that simple?

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It does not make sense that they would take a fuse that is made to protect a circuit and put in a relay which does not protect it. Are you sure they didn't replace it with a resettable circuit breaker. It seems that it is possibly the low cutoff switch or something shutting off the compressor. Also sounds like it might be low on refrigerant and possibly freezing up then shutting down till it thaws and then coming back on.

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I suggested at the plant that refrigerant was the issue and they scoffed that off. I'm electronically ignorant, so I may have misunderstood their explanation on their "fix". But they pulled the standard 15 amp fuse, and moved the replacement to another position. The device they installed has prongs just like a regular fuse, but the body of the part itself is about 1" to 1-1/4" long. Labeled BUSS with multiple numbers.

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Sounds like the OP is describing a self resetting circuit breaker, that was installed / wired into the system.

One needs a little more information regarding the systems current operating parameters.

Sounds like a pressure issue and one needs more information on the range of the parameters.

The AC unit compressor for the dash air is driven by a clutch system that is electrically controlled.

The compressor clutch circuit is controlled by the on / off switch, temperature control, low limit switch pressure switch and the high pressure limit switch in most cases.

The condenser system is cooled by air passing through as one drives down the road and is supplemented with a cooling fan mounted on condenser assembly to move air over / through the unit when the vehicle is not moving fast enough to properly cool it. This fan is thermally controlled and is wired parallel to the compressor circuit.

The system stops when the pressure drops to low or gets to high. Generally a case of the system pressure. Loss of the condenser fan can cause pressure to exceed the high pressure limit!

When the evaporator ices up air can not freely move over the area. Loss of cooling results.

The drier assembly or the evaporator orifice can ice up if the pressures in the system are off. This causes a high or low pressure issue. The system shuts down until the blockage clears, the pressure balance returns and the system will run again.. It constantly cycles !!!!

High humidity is an issue that can cause icing of the evaporator and or in the duct work.

Quote: The ambient temp seems to be a factor in the frequency of the problem.

A temperature drop of 15 to 20 degrees is normal, but as temperature rises the difference between outside temp and duct temp numbers will decrease at the outlets.

Rich.

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