Recently my cooling fan behind the radiator won't turn off. I have to disconnect the battery when the car is off just so it doesn't drain the battery completely. I already replaced the fan on/off sensor on top of the engine block and it didn't do anything. Any ideas on what I should check? I know that I can just unplug the fan, but at this point it's just easier to disconnect the battery. Any help will work

Thanks in advance

I would assume the fan relay is frozen in the on position?
Year model would help when asking questions

My bad, it was a little late when I posted this. Bt it's an '85 Camaro IROC-Z with the High Output 305 4BBL V8.

those prehistoric relays were notorious for melting wires and many times when the insulation melted it caused the wires to touch and kick the fan on. splice in a newer weatherpack relay

Where is said relay? I went to Autozone to buy the part and there are 3 different OEM numbers for the cooling fan relay. Is it in the engine bay, or is it inside of the car?

Is it an inline relay? Because I had thought I had found it a couple days ago but I'm not sure if it is or not. I've tried looking in my repair manual but there isn't a relay guide in it.

Its not inline. Older cars move the relays around away from the relay center near the booster. Sometimes its behind the pass headlight

There will be a bunch of similar looking relays. Identify them by wire color/size

Fan will have 4 wires, two 12ga two 18ga
ORN or RED 12ga
BLK/RED 12ga
TAN/WHT 18ga
GRN 18ga

Other relays include secondary fan, fuel pump, maf, burnoff and HVAC blower fan

(vettos). Its either a bad relay or your wires melted together. I jerry rigged mine. My 86 IROC has only 1 fan. So when I got the IROC as a wedding gift, the engine over heated. Fuse was.....Ohh what the H*ll. To make a long story short, If you choose to, wire the fan directly to the fuse box. Use a source that is "hot" only on ignition. If you want, put in a toggle switch so that you have control when you want to turn the key to ignition. Be very very very carefull if you go my route. You will, I repeat, you will destroy the engine or heads or even both if you decide to drive with the fan or fans off. So make sure that you switch back to on before you turn on the Camaro. My method is not the best but it will take care of your fan issue at hand.

So I replaced the relay and it still stayed on. I'm being told now that the ground wire is touching somewhere and that's what's tripping the fan. Sound about right?

No, the relay has a battery 12v input and a fused 12v IGN input

Once the IGN is removed the relay should deactivate. If the relay was improperly wired wrong and both 12v input are from the battery, then having the ground call wire touch ground even when its not supposed to will cause the relay to engage

Disconnect the control wire to the fan switch in the head and see if it stops.The switch may be bad ( to ground full time )

The switch that you mention here is the temp switch right,? Similar to this one right?

I'm not sure if we are talking about the same relay. I switched out the relay that is mounted with two screws, driver side, next to the windshield wiper motor in the back of the engine bay. I put a brand new one on and it stayed...

As far as the temp sensor, that is the one that I replaced and it didn't do anything. I have not yet tried to disconnect the fan itself. A friend of mine (who usually works on the car when I can't, legit mechanic as well) looked at everything, traced the wires and he is saying that it's probably the electric motor itself that is shorting and causing it to stay on. I bough a new motor and I'll see how that works out once I install it. If that doesn't work then we'll go from there. Probably won't do it until tomorrow since today's C-Eve though....

3oh3 Cruiser, what type of Camaro do you got?

Yeah, that's the relay that I tried. Which one is that one then? I went to Autozone and that's the one they gave me.

Anyway, like I said earlier, I have a 1985 IROC-Z, 305 c.i. High Output 4-barrel Carb. VIN G

Any other info you want about it?

Also I'm replacing the electric fan motor tomorrow, my mechanic friend says it's probably the fan itself that's shorting and keeping it on as the ground wire is fine and isn't tripping on anything.

Not sure about yours but mine had a three different temperature sensors/switches in it, one in each head and one on the intake. Before going around chasing parts you could test all of the components to determine what the problem is.

Not stock anyway ,it may be a aftermarket switch

The stock CTS (Coolant Temp Sensor ) that gives engine temp info to computer on injection cars looks like that one; mounted in intake under TB.
The switch for the fan is in the head .Looks like this
https://www.thirdgen.org/forums/post...692-post2.html

agree with above, there are three temp switches. Do you have the dual fan system or single fan (I'm guessing single). Take a test light, when you find the correct relay, and see if the power is staying on from the ignition switch to the relay, the problem might be in you igntion switch. Also, it is probably not a bad fan motor causing it. To find the right relay, hook you battery up, and pull the relay out, when the fan stops that's the right relay.
I can't remember the purpose for each of the three coolant temp switches, but there are two in heads and one on top of motor. Maybe someone can post and tell us which ones controlls the fan. I didn't think it was one on top of intake, I think it's one in the heads, but I could be wrong bout that.

Early cars only had a mech switch for the fan.
Later cars control the main fan from the computer ( from the CTS in intake under the TB ), some years (85?) had a mech switch as a backup/over ride or in later years for the 2nd fan and you also have the temp gauge sender unit

Won't be that either because relay is operated by going to ground through temp switch or A/c pressure switch ; see diagram below
( assuming stock wiring; always a bad thing on cars this old )

Doesn't work.
The fan gets it's power from the relay; not direct from the battery .If fan was shorted it would still have to be getting power through the relay to run fulltime.
Disconnect your fan relay and the fan will stop; regardless of whether it is shorted out or not
Typical fan wiring ( non computer control )

Yeah not sure about the 85, I was checking the wiring diagrams on autozone, there's a one that goes to the ECM, one that goes to an indicator lamp and one that goes to the gauge, unless I'm not reading it correctly. I do agree that the motor is least likely the problem.

So it definitely isn't the motor, ruled that one out. Mechanic's looking at it to try and find the bad relay. He's suggesting putting in a manual switch in the cabin, but I'm reluctant as I don't want to forget to turn the fan on and kill my engine by it overheating. I appreciate the diagram, but I don't know how to use them well, I'm not good with wiring, etc.

To answer a couple more questions, it is single fan, just the one behind the radiator. The fan stays on regardless of the key being in the ignition. Again I have replaced one of the temp switches and that wasn't the problem obviously and we'll see what else is going on with it when my friend comes over. I appreciate all the help from everyone though!

Man, there's A LOT of misinformation in the posts above especially confusion between models. You should have the L69 the carbureted 305. Your fan is controlled by the flat, four wire relay near the booster. The relay engages when the signal ground wire is closed either through the temp switch in the passenger side head or through the AC control head. Your relay recieves a constant hot line voltage directly from the battery (through the starter terminal) and passes it to load when two (2) things happen: It receives a 12volt/ignition on signal and the signal lead is grounded.

For it to stay on constantly power must be getting to the fan motor. Fan motor failure could not possibly cause this. Most likely cause was mentioned at the start: power load and line wires shorted at the relay.

Failure of the temp switch or short of the ground lead could NOT cause this unless there's another failure in the system (relay also receiving false ignition on voltage signal. This means TWO things failed at the same time.

UNPLUG the relay. Does it still run? You have two similar looking relays there. One controls the fuel pump the other your fan. Did you inspect the pigtail as was suggested above?

You'll find that either the relay/pigtail is bad or someone has boogered your wiring up. Use a DVM to verify that the relay is only receiving 12volts signal (on the smaller wire) when the ignition is 'ON' and that the ground signal wire isn't shorted to ground. The larger gage wire should be constant 12v the second larger wire should only pass 12v to the fan when the relay engages.

If the relay/pigtail is bad it's not worth trying to fix it. Take the advice above and replace it with a newer style relay and pigtail.

85 carbed, sorry man. Im not to familiar with that set up. Ive got the TPI setup and the relay that I posted is for the Fuel Pump or Mass Air Flow Burn-Off Relay. I knew that that relay can be used as a common relay but thats why I asked what kind of Camaro you had. Good luck bro. I hope you find the issue.

naf, I think I love you. I found the problem, it was a relay that had fallen down. Also has 2 bolts that hold it in place, it however fell down because the mounting plate broke off and the relay itself was somewhat buried within other wires. Anyway, I found the relay, unplugged it and the fan turned off, and I replaced it yesterday. Thanks for the clarification on a lot of things and I hope you had a great New Year's!

Glad you got it.