I did a lot of major work to the vehicle recently and now the primary fan is not energizing. The aux fan starts blowing per dash-readout around 240-245 as it should but, the primary never gets energized before this or while A/C is on. The plug reads 0V in all circumstances.

The primary power wire on the relay next to the primary fan on the radiator shroud is energized and I swapped it with a new relay with no success as well.

work performed prior to failure;
I replaced the 192F T-stat with a 180 but coolant is flowing, it probably needs to be packed as I get a low-coolant light.
I also recently tore down the entire dash assembly which included removing the ECU from it's harness but this is the only problem that has manifested out of nowhere seemingly.
I did run a large wire down to the power fused connectors by the battery but everything is still connected down there and again, it's only the fan that doesn't work


I also did an AB ALDL test and the fan cable does not energize.
I swapped the 30A fuse for the power A/C on the relay with the 35A defrost and it does nothing to energize the cable on AB ALDL test.

I really don't know what else I can do here, unfortunately I can't find my FSM to try to determine if the wiring is good but I would find it very odd if it were a wiring problem. The car sat undisturbed and worked perfectly prior. I would go out and replace the ECU temp sensor but if the fan isn't energizing with the AB test it would seem that's not the problem.

 

Properly bleed the coolant. I suspect the sensor is immersed in air, not coolant, hence cannot sense properly for the relay to trip. You have to do this anyway.

 

I thought of this but also thought the ALDL mode energizes the fan regardless of temperature?

 

I missed that part. You tried to energize the fan via the ALDL receptacle? My car is older, but I just learned that some later models will do that.

The first question is which ALDL connector? http://shbox.com/1/dlc1.jpg

 

yes, via connecting the A and B pins. There's a clicking noise that comes from the middle of the engine and the cel will flash if I start the car which tells me it's in diagnostic mode but it doesn't energize the fan which from what I e read, it's supposed to.
You do this with the port under the d/s dash. The fan should also be energized when the a/c is on but it's not.

 

You didn't mention a year, but I assume it's an L98 based on your avatar. The fan relay should be mounted on the rear of the wheel well under the master cylinder. You can take the cover off and close the relay contacts with your fingers. The voltage is too low to shock you. Things changed in 1990, so this might not be accurate for you if you have a later car. Here's your guy (your relay might look slightly different -- later relays are rounded):



The fans are powered through a fusible link (behind the battery). You might have a blown link. Check them out for crispiness...
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Here is some info from my 86 manual.

http://members.shaw.ca/corvette86/Co...%20Control.pdf

The fusible links for cooling fans on my 86, come off the positive battery cable. They are both orange and come off a splice barrel, just a few inches from battery terminal.

 

hey so it turned out I had been diagnosing the wrong relay!

I had thought that the relay pictured was the horn relay, but I swapped this one with a new relay and into-presto! Fan works!

I really need to find my FSM :S

thanks everyone!

 

Those relays are identical and can be swapped for troubleshooting.