Engine Fan not cutting in

Cooky3 · Post by **Cooky3** » Sun Aug 19, 2018 10:20 pm

Hi all. After some advice.

Car in for MOT last week, but test was aborted as engine overheated on ramp during the test. Never had a problem with overheating since ownership (other problems yes) or through summer. Oh, and rear brake line around fuel tank was a fail too as heavily coroded (no advisory on last MOT either and had light use / garaged since...) but a different story along with headlight bulbs flickering apparently!

When should the fan operate? I have topped up the coolant, and ran the car stationary on Saturday. Up to temperature and sat on drive for about half an hour idling with temp in centre of temp gauage as normal. At about 40 mins, temp suddenly started rising so switched off.

Any obvious places to start looking? If the fan does / doesnt kick in when aircon on (will check tomorrow) what does this mean either way?

Is it likely to be a faulty temp sender / sensor or something? Is it this green wire I have read in another thread perhaps that is the cause?

Pain in the proverbial....

Mr Tidy · Post by **Mr Tidy** » Sun Aug 19, 2018 10:29 pm

I can't help you with the fan issue, but I had advisories for rear brake pipe corrosion on mine for 2 years.

So last year I was visiting a friend in Cheshire and took mine over to Ducklakeview in Merseyside and he replaced both rear brake pipes in copper for very reasonable money (and cut and coded a flip-style key for me).

I went to the same place for my MOT this year - no advisory! And the tester was very complimentary about the quality of the new pipes - result!

FWIW I'm sure he could sort your fan issue too, although I realise you aren't exactly local to him!

Cooky3 · Post by **Cooky3** » Sun Aug 19, 2018 10:42 pm

Cheers Mr Tidy. No brainer if nearer, but just too far away unfortunately. Need a Ducklakeview in Cambridgeshire....

markplant · Post by **markplant** » Mon Aug 20, 2018 8:43 am

Remove cover above rad an check the small green wire on the top left, it's in a connector with 2 lager cables iirc

: IMG-20180818-WA0000.jpeg (186.5 KiB) Viewed 557 times

You may be able to see in the picture
As these are prone to breaking

dhobbs · Post by **dhobbs** » Mon Aug 20, 2018 5:22 pm

As said above, the small green wire corrodes and turns to dust (literally).
You can get a new crimp from BMW for less than a quid, and a little time to splice in a new length of wire.

I've just done mine after two renowned specialists couldn't figure it out!.

dhobbs · Post by **dhobbs** » Mon Aug 20, 2018 5:23 pm

Don't be fooled it's the fan, they are £500+ so best to try the wire first.

markplant · Post by **markplant** » Mon Aug 20, 2018 6:37 pm

Pic if it helps

: 203864422.png (889.47 KiB) Viewed 543 times

Cooky3 · Post by **Cooky3** » Mon Aug 20, 2018 9:05 pm

Thanks all for your help..

I'll have a look. And incidentally, turned my air on on this morning and checked to see if the fan was operating and it wasn't... The aircon was cold and working however.

So this little green wire stops the fan from kicking in when it should then?

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