The electric fan in my 84 z28 now turns on when the key is put in the on position and wont stop running until the car is turned off. It just started doing this, normally it would come on around 220 degrees then shut off when the engine cooled down. Any ideas how to get it back to normal? It's draining my battery doing this...

 

Unplug the fan switch wire from the sensor in the passenger side of the block and see if the fan turns off. If it does, the sensor is shot and needs to be replaced.

 

alright thanks ill give that a shot

 

Still having this problem guys, the sensor is brand new and the fan still turns on with ignition. I took the computer off my L69 could this be why? Or is the fan its own system? Or could I just run a toggle off the wire from the sensor to the relay and just turn it on when I want?

 

Did the fan quit coming on when you unplugged the wire from the sensor?

Is the wire in good shape? (no spots that are melted, burned, chafed, crumbling, etc.) Not touching the exhaust?

 

I have this problem myself I thought it was hard wired to stay on by the previous owner but it's all wired correctly I haven't changed anything just yet but will watch this thread!

 

I have the green wire from the sensor cut while trying to put in a toggle, but with the key on and that wire cut the fan still turns on. Could the relay be bad? I didn't see any bad spots in the wire or in any of the 4 wires actually.

 

Yes, relay contacts could be welded causing the fan to stay on.

RBob.

 

Actually, since the fan relay has power at all times from a fuse link. If the relay were welded, the fan would run all the time, not just when the key is on. You must have cut the green/white wire close to the thermal fan switch and left the AC control head connected to the fan relay. Try disconnecting the green/white wire at the AC control head. The AC switch is either stuck on or the cooling fan control circuit is shorted to ground in the AC control head.

It is much better to keep the fan controlled by the thermal fan switch than to have it on a toggle switch where you can forget to turn it on one day. You can even get lower temp thermal switches.

 

Where is this AC control head? I cut it about 6 inches from the sensor

 

If the AC was stuck on, then the fan would run continuously, not just when the key is on.

 

do you have the heater control in any of the "AC" positions? put it on "heat" and see if the fan goes off..

 

In fact no it wouldn't. The fan relay's primary circuit or coil is activated by ignition on power and then grounded by either the thermal fan switch or the AC switch. The only way the fan will run constantly is if the relay is fused in the closed position. Where as if either the thermal fan switch or the AC switch are shorted to ground or stuck in the closed position, the fan will run with the key on but not constantly, as there is no ignition power to the relay with the key off.

 

Well, I can't remember the last time I used the air, but I thought the fan runs while the air is on.

 

This is correct. The fan will run with the AC on. Later designs have the fan run only when the AC Compressor clutch is commanded on. The 84 is more simple and just has the fan relay activated when the AC switch is closed in the control head.

 

I did remove the ac not to long ago...along with any wiring that went with it. Is something missing making the fan run all the time?

 

Trace the green/white wire back to the dash, where it would have connected to the AC controls. It is probably grounded to something along the way or at the switch. Did you delete the AC controls too? I know that when I deleted my AC, I left the control head in the dash alone. Look at the wiring there for the green/white wire. If it's connected to the AC controls, disconnect it.

 

I'm having the same issue with my 91 Z 1LE. Fan goes on immediately. I don't have AC obviously so should I change the relay? I also have an check engine light on but even when I jump the ALDL I can't retrieve codes. Light is on solid. Any chance they are related?

Thanks.

Kris

 

Yes, ECM is in limp mode which turns the fan on as a safety measure. It is likely that the ECM is bad. It could be the MEMCAL which holds the PROM but more often is the ECM.

RBob.

 

Have you checked to see if the fan relay is still present?

When I bought my car, the dual fans had been wired to run continuously - like yours - once the ignition was on. I knew it wasn't correct but until charging problems arose a few years later, I didn't worry about it.

When I began tracing the charging problems and learned that the fan circuit is related to the alternator, I looked for the relays and related wiring and saw that all relays and wiring were missing! Since then, I've installed dual relays and a dual harness which tied everything in. I also noticed that four fuses were of the wrong rating and that circuit breaker fuses (thick square silver ones) were missing as well. Double check EVERY fuse in your box.

Below, is a wiring diagram for your 84 for you to look at:

http://austinthirdgen.org/mkportal/m...ine_wiring.gif

 

Thank you RBob. You confirmed that my starter wiring screw up did damage lol.