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Electrical fault...


expat69
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Hello,

This is giving me headache...

fault is:

- no more "alarm" when I leave key in or lights on when open the door with engin stopped

- no more rear wiper (if I press rear wash/wipe I get the water, but no wiper)

- front wipers work in normal operation, but do not work on wash/wipe (getting the water but no wiper)

I believe I've checked all fuses and they seem OK...

any pointer ?

I'm sure it all comes to one stupid little thing somewhere !!!

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Is this for your 300tdi?

If so, I would say possibly the ECU behind the glove box. I had similar intermittent problems, as well as the rear windows not going down, and when I changed the ECU, all was well...except for the door alarm which is still intermittent and now probably down to an earth problem on the switch. I've tried removing the switch but the self tapping screw is knackered and will not undo! Don't know if this happens with all of them, but the rear wash/wipe does not work when the driver's door is open.

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Is this for your 300tdi?

If so, I would say possibly the ECU behind the glove box. I had similar intermittent problems, as well as the rear windows not going down, and when I changed the ECU, all was well...except for the door alarm which is still intermittent and now probably down to an earth problem on the switch. I've tried removing the switch but the self tapping screw is knackered and will not undo! Don't know if this happens with all of them, but the rear wash/wipe does not work when the driver's door is open.

I had a fault on my Disco where the key in ignition chime did not work. Check your rear Brake or tail light bulbs, Right hand side If I remember correctly.

If it's blown then that could be your answer as they are on the same circuit.

The rear windows are caused by a dry solder joints on the ECU board, it's an easy fix, pull the ECU board out and you should see probably 3 dry solder joints, its a very common fault!. Just hit them with a solder iron tip and re insert it back into the ECU case. No need to buy a new one.

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Is this for your 300tdi?

If so, I would say possibly the ECU behind the glove box. I had similar intermittent problems, as well as the rear windows not going down, and when I changed the ECU, all was well...except for the door alarm which is still intermittent and now probably down to an earth problem on the switch. I've tried removing the switch but the self tapping screw is knackered and will not undo! Don't know if this happens with all of them, but the rear wash/wipe does not work when the driver's door is open.

Window ECU repair

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Also just realised that I dont have:

- rear fog light (the switch does not even illuminate)

- rear window heater

- courtesy lights when I open the door

Could it be linked to the "multifunction unit" as named by the Haynes Manual ???

expensive?

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See if this takes you anywhere.

QUOTE

--------------------------------------------------------------------------------

Circuit Operation, Multi-Function Unit

The multi-function unit (MFU) is mounted on the rear of the passenger compartment (???? LHD) fusebox 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

Testing.

================================================== ========

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.

+

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