Hello

I have 1987 Pontiac Trans Am GTA with the L98 350 engine. My problem is, that the left fan (driver side fan) starts to running very early after a few minutes while driving (at 160 F or lower) and won't shut off until i turn the engine off. Before one month everything was fine. This week I changed the ECM, fan switch and relai. But no success...

Does anyone have an idea? Thank you.

 

You may have a bad coolant temperature sensor (front of intake base next to thermo-time switch) showing ecm incorrect temp. Presumably there is no check engine light ?

 

I changed also the temperature sensor in front of the intake. (original AD-Delco part) the results are the same. there is no check engine light.

 

Does the fan come back on immediately if you turn the car off, then back on?

As a bit dumber question, does the CEL work ?

 

Yes, the CEL works.

The fan come on again, when I turn off the car and then turn on...

 

Does your a/c work ?

 

no the a/c don't work. but I testet the temp switch for the secondary (passenger side) fan. secondary fan is ok.

 

The secondary fan on an 87 is mostly useless unless you change to a lower temp fan switch.

My guess, if your a/c worked, was going to be the a/c fan request switch failing. A/C pressure rose to open the bad switch when engine bay temps got hot (exhaust manifolds) enough.

May be an issue that has to be scanned to see what is prompting the fan to come on so early.

 

Thank you. But I am still trying to fix the problem.

 

News from my side: When I drive a longer distance (about 15 miles and more) then suddenly the fan is stopping an everything is as it should be. It kick on at the intendend temperature. But the problem is: When the car is cold again, fan runs again...

 

Still have the problem. Primary fan is still on when i start the cold engine. The A/C don't works.

Can it be the a/c switch? I changed the relais, ECM, fan switch - no reason.

Thank you for some suggestions.