i have a 98 cavalier 58000 miles. the cooling fan only works with ac running replaced coolant temp sensor and relay. does any 1 have any ideal what else. thanks

The fan on this car typically comes on at around 230 F, which is higher than most expect. Did you get a code telling you it wasn't working? If you are not overheating while sitting in traffic, your fan is probably working fine.

I just ran into the same problem on my son's girlfriends car. They have both
told me for quit some time that it over heats. She has had it to a couple of
shops, and was told nothing was wrong.

When she drove it down (about 4 hr) the other day. As soon as they got
here, I told her to pull it in the drive way. I could hear the electric fan
running. That told me that the fan motor and relay were fine. And I didn't
see anyhing wrong.

Then I asked, if she had the AC on? She said yes. So I had her turn it off.
As soon as she turned it off, the fan shut down.

So I had her step on the accelerator and hold about 2K rpms and we watched
the temp go up, and up, and up. Getting just short of the yellow mark, I
told her to turn on the AC - to get the fan running and see what happened.
As soon as she turned on the fan, the temp started to fall.

So off to the auto parts store, to get a Haynes manual (boy is it poor) and
a new Engine Coolant Temp. sensor. That's the only thing I could think of
that might cause the problem.

Came home and put the new sensor in, and started the car. No change.
Let it almost get to the Yellow zone before we turned on the AC.

Then I spent a lot of time looking over the wiring diag. The ECT sensor
goes streight to the computer. The there is ONLY 1 output from the
computer to control the cooling fan. That works, cause the fan comes on
when the AC is turned on. Plus the temp gauge was working fine as it
did before I replaced the ECT sensor.

So today after work, I ran the codes - No codes found. Then I thought
I'd disconnect the battery, and reboot the computer to see of some
value had gotten scrambled and would be reset.

Started the car. This time I took my IR thermometer and checked the
radiator temp. I was agreeing with the temp gauge. Just about the
time the Temp gauge kissed the little white line before the Yellow zone,
the fan kicked on.

That's WAY too hot, and too high of an indication on the temp gauge
for me. But at least we now know that the fan does come on without
the AC being on.

I told my son's girlfriend yesterday, that if she starts to over heat, just
turn the AC on, and turn on the heat.

But now I realize that we both were just too chicken to let the temp
go as hi as it did before turning on the fans.

I don't know if the set point can be changed with a good computer,
not just a reader. If so, I'd like to lower the set point.

Hope this helps.

John

John T. Blair WA4OHZ email: jblair1948@cox.net
Va. Beach, Va
Phone: (757) 495-8229

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Thanks ChemMan & John for info thats same prob I have. it also is my daughters car so I dont drive it that much.if theres anyway to lower set temp for fan to come on I would like to know also