Cooling fan won't turn on - wiring issue??

[Ozark Lee]

I understand why the fan should run while the AC is on; what I don't understand is why the fan circuit is apparently completely dependent on the temp sender. It would make more sense to me to have the AC fan control completely separate from the temp sender, so that even if the sender failed (as in my case) the fan would still run when the AC was activated, keeping the car from cooking itself. I imagine the car's designers had their reasons, I'm just curious about what those reasons were.

At the end of the day the ECU tells the fan to come on and at what speed. The relevant inputs to the ECU are the ECT sensor and the high pressure switch for the air conditioner. If the A/C compressor is not engaging (even though the switch may be on) it will not start the fan.

...Lee

[apsmaas]

This may be a redneck solution to the problem but it will work. Just by-pass the relay and temp sensor altogether and have the fan run all the time. Just make sure you run the power through a switched fuse so that it only runs when the ignition is on. Radiator fans used to run all the time before they made them electric.

[Ozark Lee]

There are a lot of "Why ask Why" things on these cars. The original Rube Goldberg glove box latch and the space shuttle technology PCV "System" immediately come to mind.

It sounds like everything is good to go though.

...Lee