Hello, I recently bought a 1991 Z28 305 as a graduation gift to myself. So now that I'm finished with college, I'm in the process of restoring the car and gettin' her running. In short, the cooling fans aren't coming on. I'm troubleshooting the issue as per what i read on the forums and my service manual. However I have a slight hiccup: What should the Delco model number be for the primary cooling fan relay? I was under the impression that the two fan relays should be OE 14089936. However, the relay that is currently installed is OE 14103304. Just a side note, there is an extra relay system that is spliced into the primary fan relay circuitry. I'm pretty sure this is for the aftermarket alarm that was put in. I'm in the process of looking through schematics to figure out how everything should be wired up, minus the alarm (i'm thinking there's faulty wiring that's causing the problem)... Thanks in advance. I just want to double check before I do anything harmful to the car. -Joe

Ok, I took out that extra aftermarket relay, replaced the existing fan relays, and re-wired the primary fan relay (it wasn't wired correctly, as mentioned in my previous post).

the primary fan now comes on as it should when the car heats up, however the secondary did not. I'm going to search the forums, but in the mean time, is the secondary fan not supposed to go on at the same time as the primary? If they are, any suggestions?

Also, the fans do not turn on when the AC is turned on. Another thing to look at.

Thanks much for your help!

Keep in mind that the AC only controls the primary
fan with ECM.

The secondary fan is controlled by a sensor located on the
passenger side of the motor. Different temp on/off sensors
are available.

There are quite a few ways to set up fan control.
Read the stickies.
There is also a way to have the ECM control both fans
on and off temps. Wire change at ecm or jumper and bin
change for temp setting.
Next project

HTH

Ah-ha, i see. Thanks for your help.

Am I to assume that the secondary fan sensor is similar to the primary one?

Also, I read that a lack of freon will prevent the AC from going on; will that also prevent the primary fan from coming on as well? Or should the fan go on regardless of whether or not the AC actually works or not?

Thanks.

Fan turn on temperatures are different for driver and passenger. Driver will come on first.

Turning the A/C on should always turn on the driver side fan.

Turning the A/C on will turn on the passenger fan if you have a proper functioning A/C. When I was low on R-12, my passenger never turned on no matter what. When I fixed the A/C, it turned on pretty much immediately after turning on the A/C.

Check out my signature line. Lots of good info and troubleshooting.

Good info,

Didn't think secondary fan was controlled by anything other than the sensor. On/OFF at certain temp.

By looking at the diagram see where it is linked into the
AC switch.
Good to know, though not running AC
Now onto getting both fans controlled by ECM

Later

Sweet deal, thanks for the helpful replies!
I'll see what I can come up with now...

i was reading in on this myself and the primary fan comes on at temp of 195 and secondary should come on at 222 and was said that they do not come on when a/c is on .... read it on WIKI Answers.com

The way I read it now, is that the AC/on switch takes
the secondary sensor out of the loop and goes directly
to the fan.

The same for the ECM controlled primary fan

Later