cooling fan stuck on

[Steve E J]

Hey guys, I strolled up to my car today and low and behold the fan was running(I didn't drive at all today.) I jumped in and fired it up drove around a bunch and came home. I turned it off and now a half hour later it is still running.

It is raining like heck outside right now, I'm going to go and disconnect it, but does any1 know how to fix this problem right off the bat?

[Steve E J]

I pulled out the silver relay on the left hand side of the car-the wires run to the fan. And the fan stopped. I think the relay is ok(it clicks when I insert it meaning it is switching over). So... What drives that relay?

[Briano1234]

Well, if the ignition switch is broken, then the relay will get power.
Posting the year of cabby would be a good thing as then we could look up and tell you from the schematics.

But as that relay is exposed to the elements, they do go bad....(rust and corrosion) Suspect number 1.
The after fan run sensor is on the back side of the valve cover on a 90ish cabby, it looks like a big brass nut, that has a single wire out of it. If that wire is shorted directly to ground the fan will go on.
If that sensor went bad, then that could very well be your issue.

Have you checked all your fuses?

[Steve E J]

It is an 88 cabby, I have not checked the fuses.

[kamzcab86]

After-run relay: Just because it clicks doesn't mean it isn't faulty. The relay is wired into the sensor/switch on the back side of the cylinder head, which could be faulty.

Fan thermo-switch (in the radiator) could also be faulty.

Cooling fan relay (relay panel) could also be faulty.

The fan is running, which means it's getting power, which means the fuse should be fine. The fan is supposed to run up to 15 minutes with the ignition and engine off when the temp is high enough; this means the fan relays get power regardless of the ignition switch, but it is switched power via the thermo-switches in the engine bay.

[gull]

Have also had weird problems on my '88 due to the fuse panel being full of water. Might want to crawl under the dash and check the body above it for rust streaks. The windshield can leak onto the firewall stiffening channel, and there are two drain holes in it directly above the fuse box.

[Steve E J]

ooh, ok. I did notice a bit of rust and corrosion in some of the relays. I checked most of them and found the reason for my rough idle and hard starting sometimes. The fuel injection power supply relay was totally shot. It works quite well now.

anyways... back to the stinking fan

I figured out a few things.

I put in another relay(under the hood location) and it did the same thing.
The fuse for the fan is fine.
It is the high speed that is stuck on. With the fan relay pulled from under the hood the low speed still comes on. I don't see any fan relay on here http://www.cabby-info.com/images/Electr ... ePanel.png .

What drives the hi-speed?

Kamz: Where is the fan thermo-switch in the radiator?

I checked a wiring diagram and see that the ac switch and/or relay might be a problem. Where is the A/C coolant fan thermo-switch?

I will check Briano's after fan run sensor on the back of the valve cover tomorrow first thing.

[Briano1234]

The fan switch on the radiator is in the Radiator Drivers side low.

Yes you have top drain the Radiator to remove and or replace it.

There is a DIY on making your life easier by cutting your shrouds (ok, trimming them) to make them easier to remove.

Unplug that sensor on the bottom and see what happens.

[kamzcab86]

I put in another relay(under the hood location) and it did the same thing.
The fuse for the fan is fine.
It is the high speed that is stuck on. With the fan relay pulled from under the hood the low speed still comes on. I don't see any fan relay on here http://www.cabby-info.com/images/Electr ... ePanel.png .

What drives the hi-speed?

Oops... yeah, no relay on the panel for the fan, just a fuse. If the fan is stuck on high, I'd suspect the after-run thermo-switch since the after-run system runs the fan on high. Easy test: Plug everything back together; with the fan running, disconnect the wire from the after-run thermo-switch. If the fan stops, the switch is faulty (permanently shorted to ground). If the fan continues to run with the switch disconnected, the after-run relay is faulty.

[Steve E J]

Finally got some time to work on it now that it's dark. The car's battery was dead this morning (not sure why, the relay for the fan was unplugged).

After recharging the battery I unplugged the cooling fan thermo switch on the lower left of the radiator and it stopped the fan. So I am thinking I need a new sensor.

I also went to tighten up the alternator because the belt was squealing and found that the main bolt holding it in is missing.

[Briano1234]

Well that is probably why your battery was not getting proper charge.

Those switches usually go.

But on the bright side, you can drain your cooling system, and back flush the radiator.

[Steve E J]

ya, that's not all that bright. I did that about two weeks ago.

The battery had a decent charge in it last night, the relay was not connected so it couldn't have killed it.

Does anyone have a wiring diagram of the two speed fan system? My source only seems to have the single speed fan.

Thanks for all your guy's help by the way.

[Briano1234]

look in the back of the bentley for the a/c section.

[Steve E J]

Thanks guys, I got a the new switch in the mail today and installed it and it works like it should. yay

Then I was sealing my subwoofer boxes and the screwy driver slipped while putting the sub back in-put a hole in the foam surround material. Gaaa

[Calimus]

A little black RTV can help fix the speaker foam issue. It's flexible and I've seen many repaired with it from such accidental dropping of screw drivers.