Disco 1 Odd issue, not sure where to start!

ok as the titles says this is a bit of an odd issue, i've recently hit an intermittent issue with my rear wiper, read fog and rear heated screen. don't lots of searching and found out about the doors being closed tidy. tried that and it worked YAY all sorted..... NOPE

it randomly seems to decide if it wants to work or not opening and closing the doors makes no difference, something i have noticed is from time to time it all comes back to lift while im driving. and the illuminations on the buttons/switches all seem to work fine (other then the orange lite saying there on).

is there a common earth somewhere i should be checking first. got me kind of confused how the 3 all seem to go and come back together and the fact the illuminations don't seem to go when the rest of the circuit does.

two other issues i have that someone here may be able to shed light on..
Diff lock light on dash done work i've checked and changed the bulb, and tested the diff lock its defiantly working. put it down to the switch. would i be rite thinking its r/h side of transfer box and could someone tell me if i need to move anything out the way to get at it.

the second issue is the driver door, where the hinge bolts is almost no longer part of the door lol by this i mean its rusted to a point im wondering if its going to drop off lol, anyone know if i can whip the door off and weld a plate to it put the hinge on something solid or would this be a pointless battle and better looking for a new door.

as always thanks for the reply's good or bad haha

First of all I would be looking for common issues; the rear wiper and the rear screen heater for instance will have a common ground wire which will connect to the bodywork, NOT to the door. I would check those points of most stress such as inside the little rubber tube grommet in the hinge of the door. Easy enough to run a temporary earth wire to check.
The rear fogs would be a different fault, but a good place to start checking would once again be the wiring, unless you're mistakenly talking about the high level brake light in the rear window, in which case the earth problem above would apply.
As to the diff-lock light, I wouldn't know, I don't have a Disco 1 or CDL.
The driver's door hinge repair I would suggest would depend on the condition of the rest of the door. If the only corrosion is around that hinge then it might be cheaper to repair just that, but personally I would be more inclined to replace the whole door.

Sounds like a problem with your MFU

The multi-function unit (MFU) is mounted on the rear of the passenger compartment fuse box and has an input to operation of the following:

Heated rear screen
Heated front screen
Courtesy lights
Side and headlights
Rear fog guard lamps
Headlamp power wash
Front wipers
Rear wash/wipe

A fault can show in any combination of the above circuits
How to test it

Close all doors and the tailgate. NOTE: If the oil pressure switch goes open circuit (engine is started) during the following procedure, the MFU will exit the diagnostic mode immediately.

Press and hold the heated rear screen switch and switch on the ignition.
Release the heated rear screen switch within 2 seconds and the MFU will beep to indicate that it's in diagnostic mode 1.
Press the heated rear screen switch; the MFU will beep twice. In turn, operate each of the following switches, heated front screen, rear fog guard lamps, side lights, headlights, front wiper, and rear wiper. The MFU will beep twice each time a switch is operated.
Pressing the heated rear screen again will cause the MFU to enter diagnostic mode 2.
The MFU will provide outputs to the following in order given below:
Heated rear screen relay energized for 2 seconds
Heated front screen energized for 2 seconds
Courtesy lights energized for 2 seconds
Dim dip relay energized for 2 seconds
Rear fog guard lamp energized for 2 seconds
Headlamp power wash energized for half a second
Front wiper energized for half a second
Rear wipe/wash energized for half a second
The MFU will then exit the diagnostic mode.

Regards

Jonathan

thanks for the info guys it would seem my MFU is almost dead and causing me all kinds of random issues. and after reading on here i went out hoping to find the black one but no its the cream one lol. anyone know of a breakers in the south wales area likely to have one and any rough ideas on the price, found them on paddock but there little over £250 :O

I had to replace my MFU in 2012 at £130 from Rimmer's, but considering its powered up 24-7 it had a long life,
Second hand electronic equipment may work, may not, but electroni kit in what ever application can last for ever or not as we all know these days...

rimmerbros has them listed at £299 and thats well out of my range at the moment so going to have to take my chances on a 2nd hand one if i can get one, my plan is to take the old one apart and attempt to repair it when i have the 2nd unit. in time if i cant fix the one i take out i will be looking to replace it with a new one but rite now i have other more important things i need to spend on

@ceffyn There is a used cream MFU AMR5360 on the bay right now:
http://www.ebay.co.uk/itm/LAND-ROVE...445183?hash=item3603783b7f:g:bKkAAOSwjXRXY-AM
In fact there are a number if you search on just the part number AMR5360