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Brian Wise

Mac cxu613 fan clutch

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Hello, my name is Brian and am an a/c mechanic. I have a customer with a 2015 cxu613. The problem im having is with the fan clutch not engageing at all allowing the head pressure to sky rocket. I have ran the truck for at least 30 mins and have never seen fan engage. I do have 12v going to it but not sure which wire should have the 5 v computer reference signal. I believe im dealing with a bad fan clutch. Anyone have input that may be helpful to me?

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The easiest way to check to see if the fan is capable of engaging is to disconnect it from the engine harness and run the engine over 1000 rpm. The fan should fully engage in around 10 seconds, if it doesn't replace the fan drive. Loss of voltage triggers a limp home mode, keep in mind the fan drive will rarely fully engage during normal operation 75 to 80% is normal.

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I have a 2011 MACK CXU 613 I think my fan Clutch is bad the fan seems to run all the time so my question is could this cause my A/C to blow warm air?

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no.

fan clutch not locking will cause no ac condition at idle or while not moving. 

the ac needs airflow over the condenser to work. if the fan clutch is constantly locked it will be blowing air over the condenser cooling the refrigerant. 

i would suspect low refrigerant level.

with the ac on, is the clutch engaged? 

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There are 2 types of electronic viscous fan clutches, the Borg-Warner and the Behr type fan clutch. The Borg-Warner is huge and probably what is on the engine. As stated above, unplugging the B/W fan clutch should engage it within 30 seconds according to service info (usually happens immediately). If the engine is equipped with the Borg-Warner fan clutch and it does not engage then it must be replaced and updated to the smaller Behr type fan clutch and kit. It also needs to have the EECU software updated. 

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