gejettest

Hello,
1994 Cavalier with 2.2 4 cyl., 64,000 miles, in the family since new. I've inherited this car from my mom.
Issue is, why does the computer wait to turn on the fans when the temp goes all the way to the red (260 deg. F)? We have changed the temp sensor, thermostat, radiator, coolant, etc. The 'check gages' light comes on warning of a limit exceeded.
Even new computer with E-prom. Turning on the A/C turns the fan on. But without the A/C on, the computer seems to wait way too long to turn on the radiator cooling fan. This is very frustrating in city driving. No problems on the highway, plenty of airflow to keep the temp normal.

plano-doug

I suspect the issue is one of the fan relays. Not sure on a 94, but on all my other GM cars (including a 97 Lumina and a couple of 02 Impalas), there are three relays controlling the two fans. If one relay is out, you can lose one of the lower fan speeds, but still have the higher speed. That would result in the symptoms you have, that the engine gets very hot before the PCM commands the highest fan speed setting.

BTW, the 4 fan speeds are: off, both on very low (~ quarter speed), one on high, both on high.

HTH.

Doug...my first post here...

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gejettest

Very good theory. I have been troubleshooting the problem systematically and have come across 1 relay. Found the high amperage lead discolored and signs of overheating. Replaced terminal and relay. Works well when commanded to do so.
I have only 1 cooling fan, therefore 1 relay.
I will look into the possibility of a low speed relay, makes very good sense.
Thanks!