Quote:
Originally Posted by SD1too
Hi Andrew,
Here's a simplified guide to testing the 3 speed fan. - To test the low speed, press the windscreen demist button with the ignition on (or engine running). The fan should run continuously.
- To test the medium speed you will need to identify the trinary switch connector and join together terminals 2 (black wire) and 3 (yellow/grey).
- The high speed cannot easily be tested.
Things to bear in mind: - As Arctic says, with a failed low speed it's extremely likely that the medium speed won't work either. This is because they share an earth brush and it is this which wears down first. Even if you're lucky and the medium speed is still working, it will not enable the air con. to work efficiently at low road speeds.
- With a diesel there is no point in relying on the high speed. It will never be triggered since it requires a coolant temperature of 112 C and is not used by the air conditioning at all.
- Air conditioning isn't only for hot summer temperatures. Its dehumidifying effect is useful all the year around to stop the windows misting and making the interior a more pleasant place to be, and you get plenty of moisture in Scotland!
The fan systems are quite complex and differ depending upon the engine type. I have a 3 speed system like yours and I renewed the motor brushes a long time ago now and it's been totally reliable. It was then that I investigated the various circuits and I have a file full of technical information on them! The diesel is unusual in that it uses PWM decoding electronics to drive the relays and that in itself can be a source of trouble.
If you're technically minded you can restore your fan motor to working order for about £20 by buying a set of brushes from Engineering Carbon Products Ltd. Arctic has posted one of his excellent pictorial guides to the work involved.
Simon  |
Thanks, Simon! Judging by the temperature test I did yesterday with the onboard diagnostics I understand why the high fan will probably never be needed unless I have a cooling catastrophe.
I don't know if I would describe myself as technically minded
I have fixed a lot of things on my cars from mechanical stuff to the silly stuff like leaking boots but my achilles heel has always been electrical issues and faults. I simply do not understand that side of things and so far have made no effort to understand them. Silly really as cars are full of electrics.