Moved-To-TN

new member/owner of 1985 C4 my aux fan the one in front of radiator came on as soon as I turned on the key and stayed on, I found a sensor on passenger side that had no wire attached. I found a single coming from under motor grounded to a valve cover bolt. That cant be right LOL took wire off fan stopped. Question is why would you do such a thing? the other fan runs fine and cycles with engine temp. car does not overheat. should I just get a new connector for the unused sensor. maybe sensor went bad don't know Thanks for help

WVZR-1

I believe you wait until your 'manual' arrives and confirm many things among them being the AUX fan wiring!!

In your dimmer thread I asked what you bought for a manual GM/HELM FSM or something 'other than'. What did you actually purchase!!!

Moved-To-TN

I bought the 1985 corvette shop manual ST-364-85 it has red cover I am sure that wire controls fan because when I took it off the valve cover fan stoped

xrav22

I believe the wire is substituting for the aux fan wire. Very hard to test aux fan because it turns on at 238. I put a 210 sensor so it goes on well before my regular fan.
If the original single plug wire is down there you may just hook it back up. the fan is just getting a permanent ground by using the valve cover screw. Probably trying to keep the car under 228.

WVZR-1

I believe you worry about 'NOTHING' until the manual is 'in hand' and then set about proper diagnostics.

Is the SPID (Service Parts Identification) label in the storage compartment behind the seat? If yes I believe you start with verifying the option content to the car. If you find V08 then it's correct to assume the AUX FAN is OE and then you set about confirming relay, switch and wiring. If there ain't no V08 then who knows how/why it was wired!!! What color wire did you find? That would explain more! It's likely safe to assume that if wire is DK GRN you start with a new connector to the switch that should be rear of right cylinder head. MAYBE the PO had a very good reason to do it!!!

Moved-To-TN

yes I do have a V08 so I will get a new connector coming I would assume the sensor went bad so I may change that out as well

WVZR-1

I'd think there's many reasons to do just the connector first !!! I don't believe any here on the CF would recommend the switch as a 'maintenance item'!!

Moved-To-TN

definitely connector first but I was just thinking op wired it ON because switch went bad

playsdixie

That was the easy way to turn the aux fan on....just ground that wire. I ran that wire to a grounded switch under my dash so I could turn it on when I wanted.....It really does no good.....can't tell any difference and I drive in S Fl in heavy traffic sometimes......useless option.....

jseremba

The aux fan will not cool the car.
I found a sensor on passenger side that had no wire attached. I found a single coming from under motor grounded to a valve cover bolt. That cant be right LOL took wire off fan stopped. Yes it is correct because the sensor completes the ground. And that turns on the fan. By connecting the wire that should be on the switch to the engine the fan is grounded just like it would be if the fan switch were connected.
Question is why would you do such a thing? the other fan What is the other fan. One of the cooling fans against the radiator or the aux fan. Remember if the AC is on the fan(s) turn on. The fan switch is in the cylinder head passenger side and is factory set at 238 degrees. I bought a 210 switch for mine and I added an external oil cooler.

runs fine and cycles with engine temp. car does not overheat. should I just get a new connector for the unused sensor. maybe sensor went bad don't know Thanks for help

When I had this problem I took the sledge hammer approach. I bought the relay, switches and sensors and replaced them all.
Relay 15.00
Switch 18.00
Sensor 15.00

All fixed