Radiator fans won't turn off.

[bedhedned]

This problem has been on and off, sometimes my radiator fans won't turn off, even after the car is turned off. I have to disconnect the battery to get them to turn off. I've also had this same problem with the A/C blower. Sometimes the problem goes away but it's really annoying and I don't want the fans draining my battery while I'm away from the car. If it makes any difference I have the Delorean Northwest radiator fans, though they plug into the same wiring so I don't know why that would matter. Any help would be appreciated.

[Farrar]

There's a temperature switch in a coolant pipe to the left side of the engine with two wires connected to it. If you disconnect one of those wires, do the fans turn off? (You do not have to have the engine running to perform this test.) If the fans turn off, then that switch has failed "closed" and needs to be replaced.

There are a few diodes in the cooling fan system, but I would check the temperature switch first. It is also called an "Otter" switch after the company that manufactured it.

Also, welcome to DMCTalk. :)

Farrar

[TTait]

There are two devices which can turn on the relay (or relays) for the fans, one is the otterstat temperature sensor, as mentioned, the other is the air conditioning mode switch.

Both of these items however have their power supply turned off when the key goes off.

It is possible that its the AC switch or the temp sensor, but only if the car has been rewired, or if the main relay has gone bad (if that was true, then you would likely see all sorts of weird stuff going on).

I'd say the most likely cause is that the relay for the fans (see this page - post #6 http://dmctalk.org/showthread.php?40-All-Wiring-Schematics ) for the location of the relay (its #26 in the diagram).

You can swap it with #23 and see if the problem continues.

This is a typical relay to fail early as it passed a lot of current through it when the oem fans were installed and they are hard on the relay.

If you haven't updated all your relays recently, its probably time to do so.

Tom


PS - Farrar, have you ever owned a TVR or a Jag?

[sean]

Are you running an "fan fix" units? If you are unsure you can post a pic of your relay compartment and we can tell ya.

[Bitsyncmaster]

I've also had this same problem with the A/C blower.

This would make me think your AUX relay is not shutting off.

[Mike C.]

Are you running an "fan fix" units? If you are unsure you can post a pic of your relay compartment and we can tell ya.

That's what I was thinking. I recall there was an issue with one manufacturer's unit, but not sure which. On occasion, the fans would keep running even after the the car was off. You would actually have to manually unplug the power to the fan fail to shut it off.

[Dangermouse]

It is also called an "Otter" switch after the company that manufactured it.


Farrar

Well, I never knew that. Thanks

[Farrar]

PS - Farrar, have you ever owned a TVR or a Jag?

No; I almost bought an 1989 Jaguar once, but have never heard of a TVR.

Farrar

[TTait]

No; I almost bought an 1989 Jaguar once, but have never heard of a TVR.

Farrar

"Otter Switch" is very common in those circles. Less so on this side of the pond.

[Farrar]

"Otter Switch" is very common in those circles.

Oh, yes -- I learned about the Otter Switch by reading Jaguar and Lotus message boards. Some Lotus (Lotuses? Loti?) from about the same vintage as our cars even have a "fan fail" light (and wouldn't you know, they have a problem with the module breaking!).

OK, enough off-topic comments from me -- sorry.

Farrar

[bedhedned]

Thanks for all the replies, I'll try replacing the relays; I was going to do that soon anyway, we'll see if it works.

[David T]

If the fans get stuck on again first pull BOTH wires off the otterstadt switch (the temp switch in the coolant pipe that turns the fans on). It is on the left side of the engine bay in the aluminum pipe. If that doesn't stop the fans make sure the mode switch is off. If the fans still run pull the fan relays. If they still run you have a wiring problem.
David Teitelbaum