thank all of you guys for the help

Frank I installed a new temp sensor (coolant) so I have to think it is working I and as you say the relay should be fine if grounding the sensor got the fan to run. I will bypass the dryer switch this weekend and see if I get the fan to run but I thought it should always run when the AC is on so you are saying that that is not the case if so I might be chasing my tail as the car does not overheat an has never got to the line on the temp gauge (I think is 212 degrees) so maybe the fan has never been triggered.

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1972 280 SEL