Interior Lights Stuck on and Won't Turn Off

Hi All,

I have a slight problem with the Discovery (1994 300tdi) The other day after parking the discovery up I came back to find that the interior lights were all on although the doors were all shut! The only way to sort this was to take the bulbs out of the light fittings, since then I have done some investigation but am still at a loss as to where the fault is located.

Firstly, although I have tested the continuity on all door switches I have ruled these out due to the fact that the interior lights should automatically power down after a certain amount of time or when the ignition is switched, however this doesn't work.

Wondering if there is was a problem with the Multi Function Unit I replaced this, but the problem still exists.

Another thing which I have observed, which is a little strange is that if I am driving along and switch the front light to door now and then the light will remain off as it should but after 5 or so seconds will then turn off. Additionally, I have noticed that during this 5 seconds when the interior light is off the ignition light will also go off, but this will then turn on again when the interior light does.

Also, if you are driving along with the light on and go over a bump the lights will flicker.

I wonder if anyone has any experience with this kind of problem or has any suggestions?

Regards

Tom

I have similar on my 200tdi, have just left bulbs out for now but be interesting to see if anyone has a proper fix.

I had a look through the wiring diagram ( Haynes manual pre 95 diagram)just out of curiosity and to see if I could help and it did'nt show a reference to a MFU. I know you've looked at the switches but one of them sounds the most likely. Just a thought, but if you remove the connections to all of them and then put them back on one by one.. each time you do one close the doors then open them just to see if you can reproduce the fault.
May not be the answer, but will rule out switches for sure.

I don't think you should discount your door switches, I think you may have a switch that is going to earth intermittently and with vibration. You could try taking each of the switches off in turn, taping up the cable and seeing if the problem goes away. If it does thats your problem, if it doesn't it isn't.

Thats just wot i thought !!

I have checked all of the door switches and have also disconnected all of them and the problem still exists, I don't think this is the problem.

The MFU or Multi Function Unit is used to control multiple things on the discovery, such has the interior lights and the timeouts, the wipers and such things as the wipers automaticly turning on when screen was is sprayed and the headlight washers when the lights are on, etc.

Diagram of the circuit in question is as follows: -



Tom

I'm now half thinking that the problem may be due to a chafed cable, since if I have the interior lights on and go over a bump the lights flicker.

Question is I wonder where this could be to cause the problems which I have?

Does anyone have any idea?

Regards,

Tom

Hello again... chaffed cable is another pos', but before getting involved in finding it how about a quick look at the actual switch on the light fitting. You never know you're luck, could be shorting around the back.

Just wondering if you ever found a fix to this, as this happened to me last night, and the only fix I could find in the 'dark and rain', was to remove the bulbs.......

Anyone

Also, as I was looking to see if I could do a quick fix, the wire off the door switch to the passenger side was not connected - any idea on how to trace this wire???

did anyone ever fix this? I have just bought a K reg discovery and it happens to me to

range rover classic had control unit that you could run tests on, can't think of the damn name of it. Possible disco pre bcem could have same.

Sure someone will pipe up but think it's called MFU

http://www.landroversonly.com/forums/f8/mfu-19428/ look at this

I have completed a semi fix today, by wiring in two new rocker switches so i can turn the interior lights on and off...however means the light doesnt come on when i open the door, but i can live with that.

its a short to earth somewhere,interior lights are usually live but off until earthed,the short could be anywhere but where the harness goes through a hole is favourite for my money .....hope this helps....dave

what's the possibility that it could be to do with the alarm, when i unlock the wagon the lights come on, and is it connected to the "MFU"

Stu

It's got a lot to do with the multi function unit that's the unit that controls the interior lights when told to do so from the inputs, alarm system, ignition and door pins.

For a K reg disco that will be a 200 series which don't have a MFU fitted.

I have this sort of problem, will not go out when the doors are shut, then will not go off when I press the fob, nor does the indicators flash three times any more when I lock it, then all of a sudden I get the light on when I open the door then stays on. indicators flash every 20 minites when it is locked. help.

topgun said:

I have this sort of problem, will not go out when the doors are shut, then will not go off when I press the fob, nor does the indicators flash three times any more when I lock it, then all of a sudden I get the light on when I open the door then stays on. indicators flash every 20 minites when it is locked. help.

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follow this link Disco 300tdi Alarm / Central Locking Fault after New Key Fob

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Disco 300tdi Alarm / Central Locking Fault after New Key Fob