Hi there, I have a 1995 automatic Saturn SL. I had over heating problem, I did change the radiator, water pump, coolant sensor and sending unit. it is not overheating now but the cooling fan comes on when the gauge reaches halfway between c and 1/4. it will continue running as long as the car is running. If I switch off the car, the fan will continue running until the radiator cools down or the battery runs down. I am out of ideas plz help. oh by the way i changed all the relays and thermostat and still no help. Thank you

 

did you replace the 2 wire sensor for the ECTS AND THE CONNECTOR or did you replace the single wire sensor for the dash temp gauge?

The aux cooling fan is tied to the PCMs determination of the coolant temp via the ects and is toggled on and off via the aux cooling fan relay - which is also controlled by the PCM via a signal.

MAybe the ects circuit is presenting a much lower resistance to the PCM than it should (corrosion across connector pins?)

Connect a real time data capable ODBII scanner with an ODB I attachment in order to read real time data and find out what temp the PCM thinks the coolant is at. Checking this with the engine off on an ice cold engine should give you some rapid insight--then watch it as it warms up.

 

Thank you derf for taking time to respond to my request. Apparently I changed both the 2 wire sensor and single wire sensor. As for the pin connector, I replaced the 2 wire with a used one, still no help. I changed the two wire sensor twice both times bought new one from Advance autoparts all with the same results.

 

replace the ECTS connector with a new one (dealer only) or possibly the same connector from the IAT sensor

What is the resistance across the ECTS (two lead device) THROUGH the wiring harness when the engine is ice cold?

go find out what temp the PCM thinks the coolant is per my earlier post

 

Thanks Derf, I will do that and I'll keep you posted on my progress