QuestionMy 96 Disco rear windows are both stuck in the down position, I
read some of your previous posts with advice about taking the
doors apart, but my question is if there is a central control unit
common to both rear windows? The fuses look fine and I just
replaced the driver door window motor, so both front windows
work fine. I noticed both rear windows didn't work about two
weeks ago. Then both were functional again, so I made the
mistake of putting them both down, and there they have
remained. Since they seem to work or not work as a pair, it
makes me think the problem can't be in the doors.
Many thanks for any help.
AnswerHi Michael,
you are right about your rear windows. I too have this mysterious problem with my rear windows. Sometimes they work like a charm! As soon as I drive into town or park for the evening somewhere, one or both of the rear windows refuses to raise.
This may sound strange but I sometimes wait for about 30 minutes, restart the engine, drive around the block and only then does the rear window(s) finally close.
There is a central window electronic control unit (wecu) for the windows and many Disco Series I owners have had this same problem. If you have a spare $500(or more) you can have LR replace this for you.
I've been told by others that the wecu does breakdown over time. One owner found that the soldered joints were weakened and possibly shorting out. He carefully resoldered them and all was well again.
Another owner suggested that the wecu has some very sophisticated programming even if the features are not present. For example, when the Disco engine is turned off, a timer is tripped and the wcu allows 45 seconds to raise the windows. If a door is opened, the timer is reset but the window operations won't work. Over time, these sensors fail and the wcu may be disengaqing power to the windows randomly. Its really weird. Sort of like an old FORTRAN program.
All this is linked to another mysterious component call the MFU (multi-function unit)...others may have a different translation for MFU.
anyway...
here's what one owner has done:
"pin 3 on the window ecu gets a supply of 12 volts when the ignition is on. the voltage is fed from fuse 15. when the power to pin 3 is lost(ignition key off) it sets the timer going giving you 45 sec to put the windows up and close the sunroofs. the catch is if a door is opened before the 45 seconds is over it automatically times out deactivating the windows the door open signal is received on pin 7. this signal looking at the drawing is a path to ground when the door is open so...
so to get your windows to open any time all you need to do is get a 12volt supply to pin 3 (light green and purple wire) and cut the cable from pin7(purple and white wire)".
I suppose if you take a 12volt wire and patch it into a source that is active only when the ignition is on, you could, in effect, bypass the above security routine and open or close the windows whenever you want. This is true if the wcu (or window ecu) is the true fault.
I did something like this when my A/C compressor broke down this summer. I was 000's of miles from home and 00's from the nearest LR dealer. It was nearing 100F or 40C and my family was in need of relief. I took out my trusty pocket knife, split off the power line to the compressor, reconnected it to a 12volt source and the compressors clutch finally clicked on. LR had incorporated a fuse in side the A/C switch, I just by-passed it to get the thing to work. Not bad for a 15 minute fix...but I digress...
I hope this helps you out. If you plan to do the above, you'll need a voltmeter, crimping tool, solderless joints and some auto wire. Carefully which wire you poke...the main ECU is nearby and has a low tolerance to voltage pings. If you know a good auto electrician, have them take a look at it. Do you own a LR manual or even a Haynes manual? There are some wiring diagrams found in them.
I hope you have some success with this,
JohnMc
