Disco Electrics...HELP!!!!

Hi All

New to the forum and already after something...

I need to pick your brains ref a 1996 300 Tdi ES Auto:
Mine has stood for the last few months with only occasional exercise.
Last week I went to her and the battery was flat so I trickle charged it for a couple of days and got her going.
Then I noticed that the Heated front and rear screens, the rear wiper, rear fogs and sounder that warns you to remove the keys from the ignition have all failed.
All the fuses are OK.
There appears to be no damage (mice etc) or damp anywhere and all the wiring seems to be intact.
Does anyone have any experience of this problem and ideally a remedy?

I had the same problem on a Disco TDI200 (1994). I replaced the dash wiring relay unit (it's a little black box approx 50mm x 30mm under the steering column, often behind the fuses).

Changed it out for a new one and all the dash lights started working again.

Have a check, you should be able to open it up and check the resistance across the relays it may have been blown?

Thing is though Tom, the dash lights are OK except for the switches relevant to the items that don't work.
The rear fogs don't work at all, likewise the rear wiper and the heated screens.
The front fogs are fine and the rear washer and all the other lights , indicators etc.
It's very odd because it was fine before I laid her up.
I was wondering whether the flat battery had anything to do with it.
Maybe something needs resetting in one of those black box thingys??

well it happened on my car after the battery had died too? and like with your TDI300 some of the functions worked but others didn't. I don't think you can reset the Relays they're just PCB's with resistors and chips all over them. which can fail if they are underpowered or get damp.

I'll take a look tomorrow if it's dry.
Been in and out to it all day today but to no avail.
So damn frustrating.
Tried removing the battery earth strap and cleaning it up.
No good.
I'll let you know what I find.
Cheers Tom.
By the way...how do I access the "For Sale" bit on here?

as far as i know the 'for sale' section is for full members only.

Thought as much but I can't seem to find a "Joining" link.

The for sale section is not operating at the moment after the site was hacked. It is not restricted to anybody just down at the moment same as the gallery.

OK Stig...thanks for that.

Tom, I couldn't find the box you described but there is a cream coloured one about 50mm x 75mm x 25mm deep plugged into the rear of the fuseboard.
It appears to have a sounder in one corner and a PCB with various resistors and things.
I removed it and opened it up but it's dry and clean.
I wondered if the sounder is the one that usually reminds you about keys in the ignition??
I'm going to take her to the guy who does my servicing work this week.
I'm at a loss.

thats the box! you can pick up a relay from a breaker for £5 (well I may have dropped lucky with mine?) just pull the multi-point cable out of the bottom of yours and test a different one to see if it works - should do.

Think you dropped lucky Tom.
However, I found the only one on Ebay and paid £22 inc p + p so not unhappy.
Fitted it today and I now have everything back but the rear wiper.
I'm guessing that if the Multi-function Unit goes down, it takes everything and won't just fail on one item at a time?
If so then there is a problem with the wiper motor or relay.
At least I can have that tested as a stand alone problem.
I inadvertently shorted an earth and a live at the back of the switch last weekend and blew the fuse so I guess power is reaching up that high.
Possibly relay or motor then?
Either way we are getting there.
When I mentioned the MFU to my Landy man a light came on in his head and he remembered all about them so I bought the thing and chanced it.
Thanks for pointing me in the right direction Tom.
I would have totally bald as well as skint if you hadn't.

I would think it is your wiper motor that has died... I know this because this also happened when my relay died.
Open up the back door and pry off the rear door cover with a flat head screw driver and a 10mm socket wrench to undo the bolts on the handle (gently does it the cover breaks soo easily) don't forget the philips screw on the door handle lever, unplug the electrical wiper motor link (a three pin connector) get a voltometer (turn it on to sound function) and run it across the 2 & 3 pin of the electrical link to the wiper motor.
Then activate the wiper button in the cab, the voltometer should come on.
Don't expect the voltometer to go silent once the button is switched off - as the linkage uses pin 1 to send the off function!

Again a breaker is your best move if you need a replacement, I got a wiper motor for a tenner.

Tried that Tom but no joy.
If I put test lamp wires in terminals 1 and 3 of the 3 pin plug, the lamp lights as soon as ignition is switched on.
If I connect it to terminals 1 and 2 or 2 and 3, there is nothing.
Relay???
Also, what's the small 2 pin plug do on the motor itself?

Try again...Ignore my last.

If I put test lamp wires in terminals 1 and 2 of the 3 pin plug, (left to right as you look down at it with the spindle towards you) the lamp lights as soon as ignition is switched on and switch does nothing.
If I connect it to terminals 1 and 3 or 2 and 3, there is nothing.

you should have a signal change 2-3 on press 1-3 on release - so I would go with a relay issue. or something even more stupid like i duff button linkage... i've seen that on loads of discovery's.

have you switched batteries (remember you saying about the flat originally)? what sort of readings are you getting from the battery at idle?

Battery seems to be holding its charge OK although I haven't drop tested it or voltage tested the alternator.
I've ordered a new wiper motor from a guy on ebay (£36 delivered brand new).
Also got a new switch, relay and a few other bits I need from somewhere else.
Changing the spare wheel carrier whilst I'm at it cos it's a bit rough around the edges.
Getting her ready for this season's caravanning just in case I don't find a sweet V8 in time.
Just have to find out which relay is for the wiper motor and whether that's all it does.
It's all good Tom.
How's things with yours??

I would go looking for a bad earth connection at one of the wiring points.

There are earth connector blocks behind the kick panels (white connectors lots of black wires) check the drivers side first as all the things you describe as not working, are earthed there. Check the bolt for corrosion, then a quick spray with WD40.