Mi16 Fan Turning On Randomly After Car Has Been Turned Off.

[Ben.rallye 0]

Hi,

 

Recently for the first time the fan on my 205 mi16 conversion started running randomly after half an hour or so of the car being turned off. It comes on at its lowest speed and I have to disconnect the battery to turn it off. If I wait 5 or 10 minutes and re-connect the battery it will come back on at the same speed but if I leave it for a few hours then re-connect it, it doesnt come on.

I fitted a permanent fan switch into the system but that was installed a long time before this started so I would be suprised if it was that.

I'm wondering whether it could be a relay problem or just electrics?

 

Any help would be much appreciated,

 

Thanks,

 

Ben.

[Anthony 1,003]

Are you sure that the fan isn't working exactly as it's meant to?

 

The coolant temperature will normally continue to climb for a period after switching the engine off, and it's fairly common for the temperature to rise sufficiently to trip the thermoswitch and the fan to come on. Usually after a few minutes it will turn back off again - the lack of coolant flow means it normally takes longer than with the engine running.

 

Unlike most modern cars, the fan circuit is always live on a 205 (except diesels) and it coming on with the ignition off doesn't indicate a fault.

 

Replace the fan thermoswitch if you're in any doubt - they're cheap enough brand new.

[Daviewonder 533 3 Cars]

Most days when I pull up to work in my 1.6 the fan starts running as I'm walking away from the car. I still get told "your fans running" by people as they arrive at work even though they've heard it dozens of times before and I've told them it's normal.

[petert 601]

Unlike most modern cars, the fan circuit is always live on a 205 (except diesels) and it coming on with the ignition off doesn't indicate a fault.

 

 

And Motronic equipped 205's. They have a system like an Mi16.

[Paul_13 212 1 Cars]

Hello mate!

 

Only thing I can think of is dodgy switch. I've got one spare if you want to try it.

 

Paul

P.s greigs cars written off

Some old bloke went into the side of him as he didn't stop coming onto the roundabout.

Spun greig 180 went over central res backwards and ended up in a hedge.

Blown all four tyres out and a massive dent in rear 1/4

Edited August 2, 2011 by Paul_13

[Paul_13 212 1 Cars]

Is this with the car stone cold?

 

Or you running it with the blown HG?

[Rob_the_Sparky 10]

As Anthony has said, this is not unusual behaviour, mine does exactly the same thing and always has done. TBH I'd rather the fans came on a bit early that I cook a head gasket from a failed fan - as has happened to me with 2 other 205s. Simple electrical failure can = expensive bill

 

If really worried then change the temperature switch. Also after it had been running for a minute or two you can start the car and run for 10 seconds or so to stir round the now cool water in the rad, this also switches the fan off quicker.

[Ben.rallye 0]

Thanks for the replies, its not the usual slow speed fan running once turned off and as you walk away sort of thing. It would come on randomly say an hour after everything being turned off. I will try the switch but the headgasket has just got so the engines coming out and I will replace related parts to new at the time.

 

Thanks,

Ben

[Tom Fenton 1,548]

You don't say what year/car, but if it is a later GTI (post 89) then it is the thermoswitch with the red band on it you want, there are a few different ones.

[GLPoomobile 958]

How long does the fan keep running for if you don't disconnect the battery?

Edited August 4, 2011 by GLPoomobile

[Rob_the_Sparky 10]

Yeah, OK so you are saying that the fan comes on with the engine cold?

 

If it is intermittant then it is going to be hard to find. When it is doing it try pulling off the fan connection and testing the switch with a meter. That will tell you if the switch is the cause. However, to be sure the fan has to be on when the plug is removed and on when you put it back on - if not then it could be a wiring issue and moving things around starts and stops the problem.

 

You have an Mi16 conversion so it is worth looking at the wiring, see if there is anything dodgy in the harness that could effect the fans.

 

Rob

 

P.S. if the problem is intermittant then I would suspect wiring rather than the switch but worth testing it anyway.

[Rob_the_Sparky 10]

You don't say what year/car, but if it is a later GTI (post 89) then it is the thermoswitch with the red band on it you want, there are a few different ones.

 

Yeah, there are various different temperatures available but I've not spoken to a dealer about them in years. At the time they could tell you the temperature of each one so you could pick the one you wanted. If you are lucky they still can, but somehow I doubt it!

[Anthony 1,003]

The various thermoswitches and their temperature ratings are all on Servicebox still Rob.

 

The red banded switch might be the one that the 205 originally came with, but personally I prefer to put a cooler switch in place to keep it cooler in traffic and put less stress on the cooling system. From memory, the red banded switch triggers the slow-speed fan at 97 degrees, and the high speed fan at 102 degrees - already past (unpressurised) boiling point.

 

I normally use the purple banded one, that is 92 and 97 degrees for the slow and high speed fan respectively, wired in such a way that the high speed fan comes on at 92 degrees. Coupled with an 82 degree 'stat and a decent condition radiator, everything stays nice and cool and that has to be a good thing in my eyes.