LT1 Corvette cooling fan issue

The neighbor's son just picked up a 1994 Corvette for a song. Its just a little under 100K miles, and seems to have been somewhat neglected, but runs well. However, it has an odd problem with the cooling fans, and a search of corvetteforum (just a search, I'm not a member, so I couldn't post a question over there) and the internet in general doesn't reveal an answer. I'm hoping a vette/GM expert here might be able to point us in the right direction:

The primary cooling fan does not appear to come on when it hits 22X degrees, nor does the secondary come on at 23X degrees or when the A/C is turned on. However, if the temp is above the threshold for the secondary fan to come on, and you turn the A/C on, then back off, the secondary fan will come on. There are no codes/CELs showing.

They initially assume it was a relay or fan motor, and they replace the coolant temp sensor in the water pump (the one that transmits to the ECU, not the guage). Nothing helped. I pulled the coolant temp senor plug, and the car threw a code and immediately switched both fans on, as its supposed to.

While I was there, I didn't check the temp through the driver information center, so if the guage is readig too high, there is a slim chance the primary and secondary fans are wired backwards, and the actual temp is only hitting high enough to turn the first fan on. Its doubtful, though, due to the oddness in triggering the fan (switching a/c on then off). Just in case, I checked the various A/C fuses, in case this is some weird way of indicating a fuse is blown, but the ones I checked were good.

Anyone got any ideas? If we can't get it figured out, I suggested he bubba it a bit, and wire the primary fan to an aftermarket temp sensor, but it'd be nice to fix it right.

I had a couple of fan relays burn out on my 95 Caprice. Worth a look there. Differnet animal for sure, but I can't imagine GM deviating much. I knew a guy who wired up his 93 Camaro to run all the time. He said fan motors are cheaper than engines.

Yeah, thats whats weird, since I can get the fans to work when I pull the sensor plug, the relays have to be working, and theoretically, the wiring from the ECU to the fan relays is working. Presumably, something isn't sending the right signals to the ECU, but I don't know what...

I don't know the numbers, but I know my Uncles cooling fans don't come on until it gets VERY VERY HOT!!! It might be just fine. I mean seriously hot.

Don't trust the dash gauge, check the DIC readout or plug in a scan gauge of sorts to get a true read out.

The analog gauges are notorious for inaccurate temp.

My primary fan comes on at like 230 degrees or so, don't think the secondary comes on until 245 or so? Secondary fan was optional and not sure it was really necessary.

probably fine

Haven't heard back on the DIC temp reading yet, but having to toggle the A/C to get a fan to come on still leads me to think something is wrong. Any other ideas?

mine quit coming on in the 91, i got mad at diagnosing it because i had good relays, good temp sensor, and a bunch of other stuff that went down the checklist in the service manual and all roads lead me to "everything is OK"

i bought a hayden universal fan controller with a real temp sensor(not the one that sticks in the radiator fin, one that sees coolant like factory) and installed it in place of the original relays. stuff works perfect now and i can control the kick on and off temps with the turn of a knob.