QuestionQUESTION: My T&C AC works fine when we are at speeds over 30mph, but when we are stuck in traffic it looses it cooling ability. I hear a clicking (rapid) under the hood and I don't hear the fans running. I think it is a fan relay but don't know how to check the relay. I checked the codes and there are none. Can you explain how to chk the relay and where it is?
ANSWER: Hi Lawrence,
If the cooling ceases it is more likely that the ac compressor is cycling on and off. I would suggest that you check under the hood while this is happening and look/listen to the compressor clutch itself. Were that cycling, the fans would cycle also, and it indicates that there is a dropping out of the ac request circuit as a whole. Let me know if that is the case and we'll check over the possible reason. The most likely reason for the compressor cycling on and off is that the 'charge' of refrigerant in the system is low, but it might be an electrical component as well.
Roland
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---------- FOLLOW-UP ----------
QUESTION: Thanks for the help. It appears that when the AC button is turned on in the cabin, the clicking sound is coming from the compressor. It is a rapid clicking sound. The strange thing is that when we are at running speed, it operates correctly. What is your next suggestion for me to check?
AnswerHi Lawrence,
You could try switching around the compressor clutch relay, located in the power box in the engine compartment/3rd counting from the rear of the outboard side of that box, with another relay that is non-consequential but has the same part number. It could be the relay is weak. Another possibility is that the voltage output of the alternator is a bit low (it should run at least 14.4v at idle so check the voltage on the battery at low rpm for that level) which would also cause a weak relay to be flaky. But the bottom line for energizing the relay comes from a pressure sensor circuit which feeds info to the engine computer which requires that the pressure of the refrigerant meets a minimum level or it cuts out the relay so as to protect the compressor. If the pressure were just on the edge of acceptible then it might cycle as you describe. An AC shop can check that possibility. So those are the causes I can identify for you to check out in the order suggested for this rpm-dependent condition.
Roland
PS Please 'rate' my answer as earlier suggested. Thanks
