Noticed this this winter when I had to drive it to work. The coolant fan comes on with the key and goes of with the key.

It never did this before. Mike Gonzalaz installed the first engine and the fan worked fine off and on with temps for 2 years. Last year I had a lower bearing go out in it and swapped the engine out with another at a local speed shop. It was all plug and play though since I had the exact same engine going in and had a Mike G harness in it.

Now its on no matter what. And I'd like to see if any of you have any input on what to look for that would help fix it.

Thanks ahead of time.

A few questions:

1. Are you able to pull the engine coolant temperature output from an obd2 reader?
2. Do you know what the on/off temperature setting is programmed into your PCM?
3. Did you move the thermostat from your old engine to the new engine or did you buy a new thermostat?
4. What temperature of thermostat are you using?

I went through this same problem with the same engine but my situation was a little different. I replaced the heads and after that I couldn't get the coolant fan to turn off. Darth Fiero had my PCM programmed for a 180* t-stat to turn the fan on at 187* and turn it off somewhere around 183*. The problem was my thermostat seemed to be opening at around 187* and other 180* thermostats I bought opened at even higher temps. I imagine your situation may be different and it would be good to get answers to the questions up above to help troubleshoot the problem. I ended up moving my pcm fan output wire from the "low" output to "high" output (one pin over on the pcm connector) which made my fan turn on at 194 and off at 190 and I haven't had problems since. This was AFTER I replaced the radiator and water pump thinking they were faulty .

YMMV and you really should look over your coolant system to make sure it's properly burped and that air isn't entering the system.

[This message has been edited by JamesCurtis (edited 05-17-2014).]

quote Originally posted by JamesCurtis: A few questions: Are you able to pull the engine coolant temperature output from an obd2 reader? Do you know what the on/off temperature setting is programmed into your PCM? Did you move the thermostat from your old engine to the new engine or did you buy a new thermostat? What temperature of thermostat are you using? YMMV and you really should look over your coolant system to make sure it's properly burped and that air isn't entering the system.

Are you able to pull the engine coolant temperature output from an obd2 reader?
Nope

Do you know what the on/off temperature setting is programmed into your PCM?
Nope I'll have to ask Sinister Performance. They programmed it.
Did you move the thermostat from your old engine to the new engine or did you buy a new thermostat?
They reused the same Thermostat.
What temperature of thermostat are you using?
195deg


I am not entirely sure of the burp procedure on the 3800 fieros. I'll have to search around.

The fan is always on though. Even after sitting for months in the dead of winter with just turning the ignition on.

The fan on condition may be coming from your heater controls or it may be coming from the engine. Unplug C500 and see if the problem remains. If so aim your troubleshooting at the heater controls. The heater isn't set to A/C or Defrost is it?

If not then look at the PCM or engine wiring.

Everything on the dash is off. I checked that first thinking maybe defrost was on causing rad fan to be on as well.

Could be the PCM I have had a few now that for some reason no matter what the temp fan turn on is set at the fan is triggered on all the time.

C500 unplugged, key on does the fan run?

I havent had a chance to unplug the c500 but did notice the fan only does come on when the engine is started. And shuts off when killed.

And not when i just turn the key on as i previously stated.

Well then the C500 test no longer will work. The engine won't run with C500 unplugged.

That really makes it sound like the fan activation is coming from the PCM since that is the only piece of electronics that knows the engine is running. You could depin Blue 6 (Dk. Green/White) to confirm that it is coming from the PCM.

Could be a bad PCM. Could be a mis-programmed PCM also.

[This message has been edited by phonedawgz (edited 05-21-2014).]

It can all be blamed on global warming. You had a record-breaking HOT winter up there in St. Louie just goes to show that climate change is real.