4.0 engine cooling fan
Thread Starter
Joined: Aug 2018
Posts: 4
From: LA
With the ECT connected, yes because the PCM does not send a signal to the High Fan Relay. Disconnecting the ECT makes the fan run. Jumping the connector does not stop the fan. In real life it should start the fan!!! It acts opposite of what it is supposed to do. New ECT from dealer and new connector still does not fix it. The thermostat opens as required. I have order a refurbished PCM
Joined: Aug 2014
Posts: 9
From: ky
I had similar issues but my fan would kick on randomly when the ac was on. Then it stopped, disconnected the temp sensor on top of the thermostat housing and it kicked on and stayed running. Decided to buy a new sensor, thought I fixed it. It ended up not working after about 20 minutes of driving. Changed the fan assembly after realizing the plug from the resistor to the fan motor was burned up on the negative side, everything’s running as it should now.
Thread Starter
Joined: Aug 2018
Posts: 4
From: LA
thanks for your reply. I checked the fan connector it was okay. Fan works well with AC and when the High fan comes on when I disconnect the ECT the Low fan relay is de-energized as it should be. I will post when I get the refurbished PCM in.
Thread Starter
Joined: Aug 2018
Posts: 4
From: LA
While waiting for the Refurbed PCM I pulled the connection on the High Side Pressure switch... it immediately tripped the High Speed fan relay and got a high speed fan operation...this also should not have happened...just like with the ECT sensor disconnect mentioned previously. Installed refurbished PCM...it did not correct the problem. Both are switches which when disconnected should not active the cooling fan.
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yiannisthegreek
V6 (1994-2004) Mustangs
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Jan 2, 2014 09:21 AM