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MG MGF Technical - Interior lights fade but stay on...

Anyone come across this one? I've looked in archive but no luck.

Pre 2000 MGF.

Mirror, footwell and ignition lights all stay on at a very low level.

If I open either door they brighten to full, then after the usual time fade but don't go out entirely.

Flat battery. :(

I'm thinking faulty courtesy delay unit. Archives suggest this is an integral part of the fuse board and would cost £300 to buy the entire unit.

Does anyone know better? Can the delay unit be replaced by itself?

I've also read that it could be bypassed to operate without any delay. How would I do that? I don't even know where it is!

Final point - after severe vandalism (glad I didn't catch him - I'd likely be writing this from a prison!) the car has recently been completely re-sprayed. I can't help wondering of they put everything back together entirely correctly.

Any pointers would be welcome.


charley hi i got my fuse board from the mgf centre for £10 look in advertisers on this board for phone number hope this helps
sr foster 81


Strange one, you say that the ignition lights stay on ? I don't think thats right. The foorwell lights and mirror go bright and then fade to completly off, but the ignition ones sholdn't be effected ?

I presume that you mean the dashboard light ?.

Sounds like you have a faulty earth somewhere, and that the current is feeding back somehow. If car has been resprayed could be the earth has not been able to make contcat with the body due to overspray.

This is only a guess, though, and how do you find it or correct, im not sure. However you could try..

Look at the footwell light. Two wires. System either works with
a) One end is earth so at zero volts, the other is at 12volts and then slowly drops off from 12 to zero, so giving the fading. OR
b) one end is at 12 volt other isn't earth directly but goes through fader device.
So either fader is before the lamp (A) or after, I'm not sure which.

Get a voltmeter and try. If its A then you could try improving the earth conncetion. However its the ignition light that worries me, and you don't wnat to connect wires and possibly fuse the lot or cause a fire.


Ah - I've inadvertantly mislead you.

By ignition light I only mean the illuminated ring around the ignition-key hole. Nothing on the dash is implicated at all.

All interior lighting comes on as it should, then fades just as it should, but not all the way out - just stays on at a low level.

I've just pulled the fuse for now - so no clock & no radio either.

Thanks for the tip on fuse board costs! That will be handy once I know that that is the answer.
C Yarwood

The Multi Function Unit controls the lights fading. The footwell lights, mirror lights and ignition switch light are all connected to the same fuse (No12) and the MFU earths the light circuit. A purple/red wire connects the MFU and the lights. A purple wire supplies the lights.

It's possible there is a problem with the MFU which is mounted on the back of the fuseboard under the drivers dash.

Does altering the setting of the mirror light switches affect the symptoms? If so check out the mirror lights. Unplug the mirror behind the trim above the screen.

Now ex MGF
Bruce Caldwell


Were any panels removed for the respray?

I agree with Brian re an earth problem, or perhaps a wire has become trapped and has created a high resistance path for the 12 volts to reach the lighting circuit.

Looks like a difficult one to trace.

Good luck!

Sam Murray

I think this one is indeed going to be a pain....

The mirror light switches don't alter anything.

Just parked up, with fuse 12 out & set alarm. Alarm sounded. It didn't want to know about double locking.

Replaced fuse and alarm fine and lights went out!
Wonderful I thought - problem gone.

Get home & original problem back! Fuse out and it locks without sounding horn & won't double lock.

Oh dear - must be time for a pint!

C Yarwood


Hope the pint went down wel, and at leaset the weathers fine to work on the car.

It is strange, I assume the alarm is connected to the door locks and hence the lights so thats why alarm goes.

Having thought a bit more, there is obvioulsy some small current leakage thats getting through via the lights. So it could be the unit that dims the lights is just not reducing all the way down to 0 volts, or that you have something else not being earthed and so leaks through the light circuit.

Your only real option is to get a voltmeter and see how it works and see if its still providing 1 volt instead of zero, or if its something else leaking through as a bad earth.

If you remove ALL the bulbs and then connect the voltmeter with negitive to battery and the positive to first one side of where the bulb would have been and then the other, whilst opening and closing the door you should find the voltage is 12 on one side of the bulb and then it slowly dies back (ie this is the diming) from 12 to 11 to 10 etc etc..

Now if it stays (with all bulbs including the ignition removed) at 1 volt or whatever (ie not zero) its the unit. However, if it does drop all the way to zero, then its a leaking earth.

Hope this helps a bit


Thanks guys - clearly I must spend some time in cramped spaces with my meter this weekend.

Went out in the car today with fuse 12 in and interior lights at low level. Did 30 miles. On the return trip the engine dies completely. Turns over fine but nothing more.

While waiting for the AA (not alcoholics anonymous you understand) I check all other fuses. I find one of the two 30 amp EMU fuses blown.

While waiting I take out fuse 12 to avoid flattening my battery. AA replaces the 30 amp fuse and the car drives home fine.

At home I replaces fuse 12 and all the interior bulbs are now fading to black when I close the doors or start the engine. I quickly put it in the garage & everything remains off. Frightened to open the f'in doors now!

This is obviously the answer - I shouldn't be opening the ruddy doors - so 24/365, roof down and vault into the seat. QED.

I know this is not the end of the matter....

Cheers for all the pointers so far.
C Yarwood

It's a long shot, but check the wiring loom from the engine compartment into the boot lid (passenger's side).

It is common for wires to fray and cause wierd problems.

Sam Murray

Just thought I'd pop this in here in case it's useful.

Alarm system test
The alarm system can be tested by following the procedure described below:
1. Ensure doors, bonnet and the boot lid are closed.
2. Sit in the driverís seat and close the door.
NOTE: The next three actions must be carried out within 2 seconds.
3. Depress the driverís doorsill button.
4. Switch the ignition on, off and on again.
5. Raise the driverís doorsill button.
If the test mode has been entered correctly, the horns will give a short beep and the engine immobilisation buzzer will sound.
Opening either door, the bonnet or the boot lid, or operating the driverís doorsill button, will cause the alarm LED to illuminate for approximately one second. If the LED does not illuminate, there is a system fault.
The volumetric sensor can also be tested while in test mode. To test the volumetric sensor, press the unlock button on the remote handset several times. The alarm LED will illuminate for approximately 1 second each time movement is detected in the vehicle.
The test mode is cancelled by switching the ignition OFF.

Bruce Caldwell

This thread was discussed between 08/05/2006 and 13/05/2006

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