MOT concern
Q
Hoping you can help me a problem on my son’s car that lining-up to be an MOT failure? It’s a 2008 Ford Focus 1.8 TDCI estate. He noticed the driver’s side, mirror mounted, repeater had stopped working. We opened it up and changed the bulb out but it made no difference. We substituted the bulb for a working one in the passenger mirror (and checked our new bulb) and the problem stayed – it’s not the bulb.
I put a voltmeter on the driver’s side and measured no voltage; although the meter did appear to catch a regular +0 to -0. Not sure if I was being an idiot, I checked the working side and measured a healthy on/off voltage. I checked the connector in the wiring loom at the junction with the mirror and for good measure disconnected it and reconnected it. Still no luck. I’ve read cars of this age don’t have relays and I couldn’t find one in the handbook to be able to look at or substitute.
Further diagnosis is beyond me and if this is a CAN system, I imagine there could be all sorts of tricks it’s playing me that I wouldn’t expect. An auto-electrician or local garage will want £65 just to look and I’m not even sure which would be most likely to be successful. Any suggestions on what I might check and then if that doesn’t work, who I should go to?
Kevin Marlow
A
I would first check the wiring in the loom between the door and the body. The short length of loom running between the two hinges is often the cause of many such problems due to its constant flexing as the door opens and closes. This is slightly backed up by the fact that although you did not measure a voltage at the bulb you did find a pulse.
If the fault were with the relay/module then the rear indicator would also have failed as they come from the same circuit (terminal 33 of the multifunction control module). From the diagram I have, the wire should be blue/red.
The outer sheathing will need to be removed to inspect the wiring, but I would expect you to find the problem in this area, if there is no problem in the loom between the door and the body. The next step would be to check the loom where it exits the multifunction control module from the passenger side fusebox.