1994 Buick Skylark

I have the following vehicle:
94 Buick Skylark
76,000 original miles
4 cylinder

The engine coolant fan will not come on when the coolant temperature rises or when the A/C is turned on. As a result, the A/C compressor cuts out on high pressure (the lines get very hot) and the engine overheats. The temperature drops and the A/C compressor turns on whenever the vehicle is in motion.

I have found the coolant fan relay, and I jumpered the always hot terminal 30 to the coolant fan motor terminal and the coolant fan runs fine. What could be the cause of the fan not coming on? Is it a computer problem? I had someone tell me the A/C sensor could be bad, but would this prevent the coolant fan from running when the engine overheats?

Thanks, Fred
September 5, 2007.

Your system is controlled by the PCM thru the temp sensor and relay if one of those are ng PCM won't turn it on, try a new temp sensor, and check the relay while youre at it. If all else fails hard wire it to a circuit thats hot with the key on!

Sep 5, 2007.
Okay, thanks. I have replaced the coolant fan relay and the fan still does not operate. Are you saying a bad coolant temperature sensor will prevent the coolant fan from operating, even with the A/C on? I guess I thought the fan would run if " either" the temperature sensor or the A/C selector called for the coolant fan to operate. But perhaps they are interdependent on each other.

Sep 6, 2007.