I have a 1984 Camaro, and i noticed lately, that the fan doesnt always shut off when i turn the key off like it should. At first i thought it might just turn off when it is cool, but 3 hours later, its still running, so i figured i would wire up a switch for it, and then have full control, but i must not have done it right, or i wired it in series with the same relay that might be causing my issue in the first place. I ran a positive from the battery to a switch, and then a wire from the fan to the switch and then a ground to the switch (ground for a light in the switch) and when i turn the key (when its cold) it wont turn on, so there must be something that tells it when to kick in and out and i need to find out what that is. It has a 305 4bbl thats been replaced (whole nother story) so anyone that might know what this is, your input is greatly appreciated!

Thanks

 

All I've ever heard about wiring an electric fan directly through a switch is, don't do it. The switches just can't handle the current the fan draws and will eventually burn it out, start a fire, etc.

I really can't help you on exactly your fan setup, I haven't dealt with one as old as yours, (this is stock?) but I'd venture a guess that you have a large gauge wire coming off the battery or distribution block (if present) that runs constant 12V to a relay. Another large wire from the relay to the fan that is also 12V. Fan motor is probably grounded to the core support, whatever.

A small gauge wire from the fuse panel that is 12V to the relay, and another small gauge wire from the relay to a switch in the intake that actually switches the relay so the fan turns on.

Now this is how GM wired the fans up later, except the ECM controlled the fan(s) different ways different years. Your small guage fan wiring sounds like it comes from a constant 12V source, or it wouldn't run with the key off.

It shouldn't be hard for you to trace/discover where the relay is, and whether or not the wiring/switching to and from it is all working correctly, or whether the relay is the problem.

In your case, it sounds to me like the temp switch has failed. Fan turns on obviously, but doesn't know when to turn off. Could also be the relay I guess, or wiring to the temp switch, but temp switches seem to be pretty failure prone. (in the grand scheme of dealign with 20+ year old cars lol) All you'd have to do is disconnect it with the engine off and fan running, and if the fan stops, you know it's the problem.

Classic case of fixing the real problem being easier than trying to work around it.

 

Odds are it's the relay, since it runs with the key off. Remove the connector on the fan switch in the passenger cyl head and see if it makes a difference. The relay is on drivers side firewall by brake booster. Should be able to find a picture on here somewhere, although if you unplug the relay while the fan is running you will know which one it is when the fan shuts off. You can make a manual override switch if you want to using the factory relay, try a search to find out how to do it.

I would not hack everything up to make your own switch, just put it back to the way it was and fix the original problem.

 

Don't know how this turned out,but! I had the exact same problem and "sometimes" stays on.. tells me it's a sticking relay. With that said,It is possible that the fan is pulling too many amps over the contact in the relay in which case it will knock out another relay by fusing the contacts together again.Time for a new fan if that is the case OR it could be just a worn out relay,tired from years of operation.
P.S. Conventional wisdom dictates use of a relay when wiring things. A negative low voltage ground trigger for the relay
is usually all you want to run into the passenger compartment.Keep all switching and connections(as many a possible) under the hood.