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What an absolutely brilliant right up.. I just did the job on my switch pack after being driven up the wall, not knowing what it was until I saw the pin test. Confirmed intermittent problem.. I araldited the pins back in and was able to do it, leaving switches complete..Cheers
Post: ** INFO ** Repairing Window Switchpack Switches
Forum: Range Rover Mark II / P38
Assigned Moderators: RRToadHall

Posted by: marty_nz
Original Content:
Part 2:

After removing the tarnishing from the underside of the button, I decided to apply a VERY thin layer of solder on them - but don't get too excited with it - if you turn it over and can't press it down for it to 'click' then you've put too much on!
View attachment 143713

After doing this, then I lined them back up one at a time, and put some clear tape on them to keep them back in place:
View attachment 143705

With that bit back on it's possible to press the buttons and test the connections, to make sure they are solid and not intermittent anymore. I have done a pin-out of the pins on the main chip on the board and will put that at the bottom of this post, or in the next one once I've finished doing a draw up of the chip. To test the buttons, use a multimeter on continuity, and put the -ve probe on the ground point for the switch pack (the bolt on the voltage regulator by the connector is a good place) and then the +ve probe onto the pin of the main chip that you are testing. You will get a reading of 000 or 001 ohms on the side of the switch you are testing (or should do!) and a reading of about 900ohms when the opposite side of the switch is pressed. If you get a reading without pressing the switch at all, then the button is shorting out, so will be active *all* the time!
View attachment 143697

Once you have tested it an happy to begin reassembly, then use your sharp scalpel/knife etc to prick holes back in the clear tape so the legs of the switch housing and light pipe can poke back through. Then push the switch back in and then use a soldering iron to melt the plastic of the legs back to hold it in place. This is where I used the cut-offs from disassembly and melted them back in aswell and used a pair of tweezers to flatten it out to make sure that it's not going to come apart again.
View attachment 143689

And you should end up with something like this:
View attachment 143681

And a whole board of them:
View attachment 143721

Once you've got the whole thing repaired and the switches are all tested, then you can put the switch caps back on, the light pipe 'octopus' back on, you can then put it back in the casing and reassemble it all... Put it back in the vehicle and test it!

Image below is of the chip that's on the switch pack - looking at it, the black dot is the semi-circle towards the edge of the board.
View attachment 143769

Hope others find this useful, and can keep a few switchpacks in use for a bit longer - since they seem to be 'unfixable'

I am also looking into the possibility of replacing the little metal 'pad' switches (if they've worn out completely for example) with the small 'tactile' surface mount switches (like the buttons in the remote fob) - but since these seem to be repairable, that's a bit further down the list again!

This won't fix the problems where the switch pack completely fails (like some people find after putting a new battery in)... I am not sure what causes this, but if someone has a spare one about somewhere which has failed in this manner, then I'm happy to take it off your hands and take a look into what has actually failed on it and see if it is repairable too...

Marty
 
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