Radiator Fans not stopping

[philmcw]

Just spent the day crusin and generally enjoying the sun - including a nice little run in with an imprezza sti - sorry mate you just wern't fast enough

Put her back in the garage and usually when I kill the engine the radiator fans stop - if they are running. This time thou' they kept running. Hmmmmm i though - maybe they keep running a bit longer so I left it.

Went out about 20-30 mins later - no, it was nearer 1 hour and they were still running - both of 'em flat out.

I took the fuse out and put it back in about 30 mins later. The fans did not start up again.

Very strange

Anyone else experienced strangeness like this ?

[yzf1070]

My best guess is that the relays have badly burned contact faces and they welded together. Basically the fan motors create a high inductive load and the relay contacts are not up to the job long term. Because the fan motors pull such a high current, when the power to the relay coil is cut (coolant temp normal), the inductive load is so high there is an arc across the relay contacts when they open. This arc burns the contact surface and essentially creates molten metal this has the effect of eventually welding the contacts together. Of course its not quite high enough to create a solid weld and in your case I suspect when you removed the fuse the spring rating of the relay was eventually strong enough to break the weld and open the contacts.

Pull the 2 relays (should be yellow) and open them up, if the contact faces are badly burned the above is exactly what happened......replace the relays.

(If you dont know for sure which are the relays...email me and I will send you a fuse box diagram).

Good luck

G

[hallsie]

If you have a fuse box diagram, any chance you could mail me it too!!


stu

[yzf1070]

hallsie said:

If you have a fuse box diagram, any chance you could mail me it too!!


stu

email me through my profile and I will send the layout to you.

[diver]

This happened to me last year. In my case it was some water that somehow got on the relays, the surface with the pins on it was just slightly damp, and that was enough to keep the fans on. I hadn't washed it just before or anything, and I had to keep pulling the relay out and drying it off for a couple of days before it stopped happening again?

It's never happened since, just another spooky TVR experience.

[philmcw]

Hi

My fuse diagram shows two fan relays : 23 & 51.

I take it this is one relay / fan ?

Thanks

[yzf1070]

philmcw said:

Hi

My fuse diagram shows two fan relays : 23 & 51.

I take it this is one relay / fan ?

Thanks

Thats correct

[philip_cooke]

So now I am having the same problems with the fan on the drivers side constantly running. I have checked the relay (and swapped it over - the relays work fine) and nothing changes, ie the fan keeps running. What gives the signal to the relay? I guess there will be a heat dependant resistor somewhere on the engine - does this then feed into the ECU? or how does the relay get its 'activation' signal? Is it simply due to the heat dependant resistance change allowing sufficient current to flow? Anyone any ideas where to go from here?

[GreenV8S]

There is a thermister on the engine, the ECU uses this to determine the coolant temperature and is configured to turn the fans on/off at set temperatures. I suggest your first step should be to see whether the relay is working correctly i.e. are the fans on because the ECU has operated the relay, or because of a relay/wiring fault.

[whitey]

philip_cooke said:

So now I am having the same problems with the fan on the drivers side constantly running. I have checked the relay (and swapped it over - the relays work fine) and nothing changes, ie the fan keeps running. What gives the signal to the relay? I guess there will be a heat dependant resistor somewhere on the engine - does this then feed into the ECU? or how does the relay get its 'activation' signal? Is it simply due to the heat dependant resistance change allowing sufficient current to flow? Anyone any ideas where to go from here?

sounds like you have a faulty trinomery(sp?) switch. Your nearest dealer will be able give you more advice and sell it to you. Cheapish from memory.

cheers
Whitey

[philip_cooke]

Thanks Peter, Whitey.
The relay itself is working fine. I have removed it, taken the plastic housing off and checked with a multimeter. Also, when re-inserting the relay into the fuse panel, it can be heard clicking (once when inserted ie when fans come on and once when removed ie when power is disconnected) There is either a signal fault (ie thermistor issue) or wiring fault which I do not suspect as the car has been fine over the last few days and nothing has been changed/adjusted/played with. Any ideas as to where on the engine this thermistor / trinomery(sp?) switch might be? I'm guessing the good old 'take it out and put it in a pot of boiling water whilst connected to a multimeter' should do the trick to test it. Any ideas as to part numbers/ratings etc?

[whitey]

last item on this page, I guess it may mean you might have to have aircon! This part was at fault when my o/s fan stayed on even with the ignition off.

www.clever-trevor.net/category2/cooling-system/7/

[philip_cooke]

Thanks Whitey - and yes, I have air con. Any ideas as to where this little blighter might be in the car? In the meantime (before I get this issue sorted) I have removed the relay so the drivers fan doesn't come on - I was expecting to see the temperature rise this morning but I don't think it got above 75 degrees! The oil got to about 65 max which I seem to recollect is a bit low for my normal drive into work, however, it was cool, not cold, this morning. I'm hoping that when the temp gets to 96 (or thereabouts) the second relay will kick in to keep the water cool - of course, it means I have to keep a close eye on the temp guage, but it doesn't move that quickly. Failing that, all I have to do is pull over and pop the relay back in!

[whitey]

don't risk letting it overheat, the headgasket is a weak point(due to the wrong head bolt washers used on many engines) and there is lack of water cooling to number 6 cylinder.

[rev limiter]

if you have air con most likely to be faulty trinary switch

[philip_cooke]

Thanks Rev, that's what Whitey said below ('cept he can't spool). Any ideas where this switch is located? I know where I can get hold of one (Clever-Trevor) I just need to know where it goes!!

[philmcw]

Hi

I was told by a dealer that if you have air-con, one / (both ?) of the fans remain on whilst the air-con is working - irrelevant of engine temp...

Never got around to testing this piece of info though !

[andyoleary]

Doesn't sound right to me, I have a/c and the fans only come on when the temp's call for it...

Andy

[yzf1070]

andyoleary said:

Doesn't sound right to me, I have a/c and the fans only come on when the temp's call for it...

Andy

Yep I concur...mines the same

[xtr2turbo]

philip_cooke said:

Thanks Rev, that's what Whitey said below ('cept he can't spool). Any ideas where this switch is located? I know where I can get hold of one (Clever-Trevor) I just need to know where it goes!!

Phillip did you find where it is located. I think I may have the same problem,.