So, having a problem with my 1989 iroc heating up in traffic. It is a true iroc with dual stock electric fans, but some modified it so the drive side fan turns on as soon as the engine is running. The second fan only kicks on when the AC is turned on. The car does have a custom chip from a local performance shop and it is set for 185F.

Shouldn’t the second fan kick on once the coolant temperature sensor hits the temp programmed in the ECM?

• I have tested the relay by grounding the green wire, but it is obviously good since the AC kicks the fan on.
• Fan is good
• I check that the coolant temperature sensor is getting voltage when the car is running.
• I have replaced the coolant temperature sensor twice

What am I missing?

How do I figure out if the ECM is sending the voltage out to the relay? Where could it be broken?

 

Your car sounds correct. The secondary fan won't turn on until it hits 235° or your have the A/C on. See my sig for details.

If you want the secondary fan to run sooner, you need a new fan temp switch (screws in between the #6 and #8 spark plugs down underneath the car.)

 

The 89 L98 TPI has the dash coolant sensor in between spark plug 1 & 3 on the driver side and the second one is in the front of the intake, correct ? The only senser on the passenger side is the knock sensor, correct ? Or am I missing that thre is a 3rd coolant temperature sensor?

I have the service manuals, but how did I figure out where the CKT 731 is located? What is CKT, I do not see that reference in the manual?

The second fan will not kick on based on temp. The dash gauge will climb all the way up to 250 and nothing, then I manually jumper the reply connector to cool the car down.

 

Ok, so I just put the front end of the car up and notice there is a sensor between 8 & 6, but there is no connector going to it. There is a black wire hanging by the knock sensor so I am assuming that is the wire that needs to be connected to the 3rd coolant sensor.

 

That's it. Here is the one I use.

http://www.summitracing.com/parts/HYP-4028/

 

ok I so now I ran a 14 gauge wire from the sensor in between 8 & 6 and connected it to the hanging wire, this is just for testing purposes and the fan never came on. The car gauge was easily 240 and no fan. I kicked on the defrosters with heat and the car temp dropped from 240 to 220.

I am lost! Can not figure out how to test ECM

 

Front of radiator clean? Mine was matted up like someone stuffed some hood insulation into it.