97 Disco 1, 173K - several previous owners. Interior light switch above windshield has on (full brightness), slightly dimmed (center position) and off. Doors have no effect on lights, they will stay on until you move switch to off position. Rear wiper does not work either. Removed rear door panel and swap wiper motor, still no joy.

Have seen other posts about rear wiper not working unless all doors are closed (courtesy lights out) to prevent rear washer from soaking inside of door if it was open.

So could my rear wiper problem actually be a door switch / dome light problem, where the MFU is being told that doors are not closed? But alarm seems to work normally.

Also, what is best way to removed fuse box under steering wheel to get at the MFU?

 

I know it sound silly, but did you check all you're fuses? I had the same prob. long ago and thats what it was.

But, if I remember right, to get the fuse box out, I used a long 1/4 drive extension with a u-joint flex thingy to remove the bolts. I believe I had to remove the foam piece that makes a U shape under the steering shaft to make more room.

Then once it's loose, it will only come out a little, and you have to reach behind it and undo a harness or two. It wasn't too bad.

 

Yea check all the fuses then all the door switches, I think its 12&13 are the mfu, but check them all. My fuse was out when I bought the truck, interior lights didn't work the rear wiper came on randomly, and so did the rear defroster, and at one point the defroster button was locking and unlocking the doors. All fixed by one fuse.

 

The electrical systems in these trucks are seriously haphazard. I replaced the ingnition/steering column lock and now the interior lights blink like the alarm light on the dash until I put the key in the ignition, then they light. And all I did was replace one part. Nutz. At least everything 'works'.

 

Cleaned all door switchs with wire brush and contact cleaner, had green gunk on one (right front). Before, with all doors closed, the test mode for the MFU would not run the rear wiper. After, the wiper runs for 1/2 second per normal test mode, and runs when dash switch is pressed, so great. I had hoped this would also fix dome light "always on" - but looks like I will have to go into the MFU for that.

Thanks to all who responded, and it is a lot easier to clean door contacts than R&R the rear wiper....

 

And after a couple of 8mm bolts removed from the fuse block (WITH BATTERY DISCONNECTED !!!) - I was able to swap out the MFU. Noticed right away on the diagnostic test that the interior lights came on for a half second, and now they appear to work normal. My creative PO had removed cargo bulb and center dome bulb, will have to purchase and install those as well.

 

Gotta love the creative work around.