Ok, about 2 months ago my fans just stopped working unless I turned the A/C on. Once the A/C is turned ff tho the fan remains on until the car is completely turned off via ignition. I replaced the sensor and now the fan kicks on at 220 or whatever the stock setting is but I still have the problem where it no longer turns off. It just continually runs until the car is turned off and restarted. I noticed that when I took the Wire off the sensor and grounded it out the fans came on and when I removed it they kicked off as far as the sensor wire goes. It just doesnt make sense as to why the fans stay on after the a/c is kicked off and the car is cooled down to whatever it's supposed to be. With the fan continually running it reaches temps of 120-130. Not good in the winter lol.

Is this problem for the '84 mentioned in your field data (under you avatar) ?

O yeah. My bad, the 84z, single electric fan.

Not a big deal, I just didn't realize any of the '84's had an electric fan so I was making sure. You said 'fans' and 'they' which was making me think it was something different.

Which sensor are you unplugging ?
You mentioned grounding it which seems to me you're unplugging the fan switch instead.

If the 'sensor' is unplugged (left ungrounded), does switching the A/C still cause the same fan run-on issue ?

I was unplugging the fan Switch. It's located on the passenger side around cylinder 6 to 8. The drivers side is my temp guage. Um, To be honest i'm not sure. I don't think I have unplugged it and tried the A/C fan while unplugged to be honest.

It's hard to say but, I can't imagine the lg4 wiring being much different from 84-87 for the elec fan.

If that is true, the fan switch and hvac control both tie to the ground of the relay causing it to switch and run the fan. It's the same way the TBI works as well.

Other than that, there is nothing else tied to the relay, for the fan, on the coil side to make it switch or hold open, causing the fan to run on. It's like you have a latching relay.

Something with the hvac is causing the relay coil to stay grounded (fan running) though until the power is cut.

I'm curious about trying the the A/C w/o the fan switch and also, running the a/c as described above and pulling the fan fuse (while still on)then reinstalling it to see if the fan quits.

Other than testing that, I'm a bit stumped, unless the wiring isn't stock.

Thank you for the input. I'll test your theories out tomorrow and get back with an update of the situation. It's a bit dark and cold right now lol.

ironically, I have pretty much the same problem, but I put in a hypertech switch.

Ok, update. I unplugged the switch and heres the results. The fan now turns off when I turn the A/C off. Plugged the switch back in and bam, fan stays on after A/C is turned off. I also noticed with the switch plugged in the fan is coming on at about 160-170 instead of 220 and remaining on until the ignition is turned off. This leads me to believe I have a faulty switch or the wrong one. Heading to the parts store tomorrow or sometime this week. I'll update with details.