My cooling fan does not come on. I replaced the fan relay with a new one, and still nothing. I ran the car up to about 215 degrees. When does the fan typically come on? How would I hardwire this thing to a toggle switch or just to always be on?

 

which car? the 86 or the 02?

List of checks to do.

Some ECM's are programmed to come on at over 215...

Turn the A/C on, does the fan come on?

Coolant sensor for the PCM, on both years it should be easily found and the same yellow/black two wire sensor. Take the wiring off the sensor, jump the terminals with a paper clip. What happens? This will and should also kick a "check engine" light and hard codes

Fuses...check them, all of them, I can't recall what the 02' circuits are and I don't have that info handy.

Some have dual temp sensors, again, it will depend on which car has issues.

Any power to the relay? Any power to the fan when the two wire sensor jumped?

This is just the beginning, need a lot more info. Not harping, but there have been a lot of coolant issue threads in the forums, do a search and you'll see many of the replies on things to check and common issues with the cars.

 

I'm sorry, I neglected to say this problem is with my 86 Iroc (305 tpi). I heard the fan comes on at 242 so I ran it hot and the fan surely comes on, around 230 actually. This seems ridiculously hot in my opinion, for a fan to come on that late. My shroud must be bent a little because the fan rubs a little bit and prevents it from spinning very fast.

 

It is ridiculously hot and the normal ECM programming for GM's.

GM has their programming on many cars to throw that fans on at temps people aren't used to seeing.

If the fan is cycling on off, and the coolant is staying at that temp then you most likely have normal fan operation. Although comparing the actual temp on the dash to the temp read by the ECM is the key to know if you are in fact running hot. GM gauges are notoriously inaccurate in my opinion and can throw you for a loop. I've seen 20-50 degree differences in gauges to ECM readings on GM vehicles.

Also with a scan tool hooked up you can see if the command for cooling fans on and off and the temp read threw the ecm and know if the system is operating properly.

If you don't like the late, hotter activation there are kits that you could hard wire in and do away with the ECM controlling the fan. Swithing temp switches or adding one that commands a relay to close at 190 or whatever you like could be put in. There should be a aftermarket chip set to do the same. A different PROM to tell the ECM to get them on sooner.

Also, if you have a Ohm meter handy, get the car up to it's hot temperature, don't burn yourself, and after the fan kicks on shut the car off, pull the ecm wiring on the two wire sensor for fan control to ECM and measure resistance across the two terminals of the sensor. Tell me that reading, and I'll be able to tell you if the sensor is ok and actually working perfect or "worn" and causing a late operation.

210----185 ohms
160----470 ohms
100----1800 ohms