Tuesday, July 9, 2013

Dodge Grand Caravan SXT Fan Not Coming ON When A/C Is ON?

Engine Cooling Fan Will Not Come ON


My fan relay is working when engine gets warm. My problem is that the fans do not come on when the ac is on and engine temp is below the trigger point.


Troubleshooting Solution For This Problem:

Before Confirming The Fault For the Problem.Understand how The Engine Cooling Fan Turns ON.


A/C Pressure Transducer:

A/C high side pressure is monitored by the a/c pressure transducer. The transducer is an input to the powertrain control module (PCM) and this is how the PCM decides when to run the fan. When high side pressure increases then it will turn the fan on, duty cycling it to control pressure.


Using scan Tool to Inspect Transducer Pressure Signal:

Obviously the fans work so the relay, fans and wiring are all ok. What I would do is use a scan tool to look at the transducer's pressure signal and compare it to what is seen on a mechanical gauge. If the transducer has failed or there is a wiring issue then it could be reporting an incorrect pressure and the PCM thinks pressure is lower than it actually is and it doesn't think it needs to run the fan.


Incorrect Transducer Signal:

If the system is properly charged even if the fan never came on it still shouldn't vent. Once the PCM sees pressure go high enough it will shut the compressor off before it gets to the point of venting. This is more proof that you very likely have an incorrect transducer signal.

This details Will Help.
Thanks.

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