Strange electrics

Hi, anyone got an idea on this one? Turn ventilation fan on- headlights come on as well! Side light switch then turns them off. Turn the fan off - all’s fine, all light switches work as normal. Can’t seem to figure out the wiring diagram to see how this is occuring. Has this happened to anyone else?


obvious q’s first… DO YOU KNOW FOR SURE that its not always done this? when did it start doing it and what work have you had done recently that may have led to it happening (if any) - it might not be an obvious link.

Another thing… can you switch the fan on with the ignition OFF ??.. you should be able to switch ALL your lights (both switches) on and off but the fan shouldn’t work with ign OFF. It sounds like fan and lights are sharing 12v somewhere and unless its always been like this the obvious candidates would be one of the switches is faulty or maybe the fuses are somehow touching ? you prolly need to get a multimeter and start logically taking measurements and removing connections in those areas.


“Strange Electrics” - is there any other sort in a plastic car ???..

…but this is definately weird and not at all right. Good advice from Rox. You need to be methodical with a meter (start with continuity between components and then check voltages.) Have you got a wiring diagram?


Hello again,
Thanks for the ideas- the multimeter is on it’s way out to the garage!
In response to the questions.
Yes I’ve got the wiring diagram, but don’t like these ones spread over about 20 sheets.
It’s only been doing it for 2 days.
With the ignition off all’s ok- lights switch on as normal.
With ignition on and fan off- all fine.
Turn fan on and headlights/tail-lights come on.
Press side-light switch and headlights off, sidelights only.
I’ve lots of experience of gradual problems developing in “plastic cars” (Elan and Plus2 with bad earths), but this is sudden so I guess a wire off somewhere.
Will report back if I find it!

Not the old cigar lighter wires round the wrong way is it?