Radiator fan won't switch off

[tman2714 0]

Hi all,

 

Came out to a dead battery this morning.

After trying to start the car the radiator fan came on so I'm pretty sure that's what drained the battery. After a very short drive over the weekend the fan came on but I didn't think anything of it then.

 

I can jump the car then plug and unplug the fan as required but what could be at fault here?

 

The brass coolant temp switch was replaced about 3 years ago. Could that have gone again? (last time it wasn't coming on)

It's a cheap and easy fix so I might try that.

 

Any other ideas?

 

A problem that might be linked is when under hard acceleration the engine temp light starts to flash.

 

As always, any help is much appreciated.

[tman2714 0]

http://the-corrado.net/showthread.php?85305-HELP-radiator-fan-on-all-the-time-with-ignition-off-draining-battery

 

Just found this.

Which is the three pin fan sender?

[dr_mat 0]

There's a temp switch for the ignition-on fans attached directly to the back of the radiator. I don't believe that controls run-on.

Run-on (and ultra high speed fan) is controlled by the small unit attached near the fly hose from the top rad hose. It has two fuses and a couple of relays in there.

Afaicr the run-on should only run for ten minutes anyway, and even if the coolant was still hot it should stop.

There is no engine temp light by the way, there's a water low, oil low, and battery not charging. Which light are you referring to?

[tman2714 0]

Thanks mat. I'll have a look at those tomorrow.

 

Oh right, I'm referring to the light above the coolant temp. Must be the water low light then. I thought it came on when the coolant got too hot?

[fendervg 33]

I think it depends on what speed the fan is staying on at, as the different stages are controlled by different sensors. When this happened to me (fan stayed on after car turned off with key out and battery running flat) it was definitely replacing the three pin sensor in the radiator that fixed it for me.

[dr_mat 0]

Thanks mat. I'll have a look at those tomorrow.

 

Oh right, I'm referring to the light above the coolant temp. Must be the water low light then. I thought it came on when the coolant got too hot?

Sounds likely you have an air lock.. this can result in superheated steam hitting the sensors occasionally. I'm not familiar with a light /above/ the temp gauge though.. presumably I never saw it come on? Which car is this?

 

You do have a dodgy run-on control unit or relay i suspect though.

[tman2714 0]

The light I have is in the attached image.

 

I'll do some investigating on the fan this evening. Hopefully its not the control module.

 

Thanks for the tip on the airlock. I'll see if I can sort that out at the same time.

 

Ugh! Only just got back on the road!

[tman2714 0]

So after getting the car started again I went for a short drive. Fan didn't come on until after I turned the car off and it stayed on for ages. When I unplugged the temp sensor connected to the radiator, the fan stayed on.

 

Must be a dodgy run-on control unit or relay then?

 

I need to check the fuses but ran out of time this evening.

[dr_mat 0]

I would admit I'm not so familiar with the early 16v/g60 cars so I may be way off with that..

[tman2714 0]

You know more than I do!

 

So I unplugged the radiator fan last night but still came out to a dead battery this morning. Might be a silly question but is the fault still drawing power even though the fan is unplugged?

 

Or is it something else?

 

I'm stumped.

[dr_mat 0]

Must be something else. General advice on power drain is to get a current meter in line with the battery if you can, and pull fuses until the drain disappears.

[Wullie 1]

I had a similar problem on mine. The fan running on turned out to be corrosion and crap in the plug at the bottom of the radiator. A thorough cleaning cleaned it out. I also had the battery drain bit as well and tracked it down by pulling fuses, from my old post on the solution " I connected a 21w indicator bulb between the battery + terminal and clamp and it lit up like Blackpool Illuminations. I made the test lamp lead long enough to reach into the car so it provided some light until I found the fuse that protected the offending circuit, it was the "Let's hide a fuse where no-one can find it" one at the top of the fusebox above the relays. I started by disconnecting components until eventually the light went out again, well fell to a dim red glow which is about normal. Typically it was the last thing I disconnected having started with the driver's door." Hope this is of some help.

[tman2714 0]

I'll have to get a multimeter and do some tests. When you say inline with the battery, where exactly do I attach it?

 

Wullie - I don't think it's the plug at the radiator because the fan stayed on when I unplugged that connector.

Where did you clamp the other end of your test bulb?

[tman2714 0]

Ok don't answer the multimeter question. I've used the wonders of Google.

[Wullie 1]

There is the plug on the fan unit itself and there is a plug at the bottom of the radiator. It was the one at the bottom of the radiator that was causing the problem. Might be worth looking at the wiring for them both as it' will be a bit brittle and aged by now.

[tman2714 0]

Thanks Wullie. The fan continued to run with the bottom radiator plug taken out. The plug and lead look ok to me.

More investigation tomorrow.

 

I don't think I have a fan control unit under the bonnet. Mines a 1990 1.8 16v.

[Wullie 1]

I don't think there is a fan control unit, I never found one though I didn't search too hard. As far as I'm aware there are the run on sensor on the front of the engine above the alternator(Brass thingy with one terminal), The sender at the bottom of the radiator an the radiator plug itself. You can test the run on sensor by disconnecting it when the fan is runniing and the ignition off by simply disconnecting the wire. The fan should stop. Don't know how it does it but this electricity stuff is new to me. Maybe someone with a bit more knowledge than me will have a better idea.

[Jim 2]

Have you replaced the other fan switch in the side of the head? Just reading this thread here that says there's one there, as well as the one plugged into the radiator:

 

http://www.the-corrado.net/showthread.php?25856-1-8-16v-fan-coming-on-when-cold

[tman2714 0]

Ok, so there could be another sensor at fault. I tried looking for it but I'm really not sure what I'm looking for. The only thing I think it might be is this:

 

 

Is that the other temp sensor? It's just loose on my car, not bolted to anything!

 

It looks like a metal (could be brass) yoyo with one spade connector in the top and a clear tube coming out the bottom.

 

If anyone has any pictures, that would massively help.

 

Due to drive the C to Glastonbury next week - will definitely disconnect the battery when we park up!

 

Thanks so much for the help everyone!

[Jim 2]

Ok, so there could be another sensor at fault. I tried looking for it but I'm really not sure what I'm looking for. The only thing I think it might be is this:

 

 

Is that the other temp sensor? It's just loose on my car, not bolted to anything!

 

It looks like a metal (could be brass) yoyo with one spade connector in the top and a clear tube coming out the bottom.

 

If anyone has any pictures, that would massively help.

 

Due to drive the C to Glastonbury next week - will definitely disconnect the battery when we park up!

 

Thanks so much for the help everyone!

 

As per the diagram wonder if it'd either be the ECU temperature sensor, or (if present) the fan over-run up top. I'd just try disconnecting the sensors one at a time on the side of the block and see if the fan magically stops running.

[Gti_Jamo 10]

I'm not usre if it's the same with the valvers but the G60's also have a sensor on the fuel rail which maintains fuel pressure if evaporation takes place inside fuel rail, this also makes the fan run on.

[tman2714 0]

I'm not sure either.

 

I'm doing some testing now. After getting the car hot:

Switch engine off but leave ignition on = fan runs for a minute or then switches off.

Then I took the keys out = fan comes on and doesn't show signs of stopping.

Then I disconnect the negative terminal fan turns off (obviously) and instantly re-connect it = fan stays off.

 

Using a multimeter (when the fan is off) I'm only getting a draw of 50mA so at least there isn't anything else drawing power.

[dr_mat 0]

Sounds like a bad relay to me.

[tman2714 0]

Yeah I think I've finally come to the same conclusion. Just got to find it!

Thanks for all the help.

[tman2714 0]

Thanks for all the help on this. Car made it OK and was still fine to drive home. Although the radiator fan comes on after the ignition is switched on without the engine, it is actually turning off after 10mins. I think the battery drain I was seeing was from the boot light. It was shorting on the bodywork but only intermittently.

 

I've got a replacement relay now in case it does still happen.

 

Thanks for all the help, couldn't have done it without you lot.