So, I've been intrigued for awhile about the issues that there are with window switchpacks - randomly failing, or switches becoming intermittent.

Sometimes, yes a blast of contact cleaner works, or it works for awhile and then it starts playing up again.

We've got a P38 in the workshop that we are fixing up to sell, rather than break it for parts - and the other day I noticed that the window switches were playing up. They had all been working fine, but now they were intermittent at best.

So, being that I like to pull things apart, and because I wanted to see if it was fixable rather than chuck it out and buy a replacement - which will be second hand anyway, I got it on the work bench this afternoon and stripped it right back. I did a test run on one of them to see if it was a case of being able to repair, before breaking out the camera and taking photos... Pix or it didn't happen, right?

What I found (before I get into the pictures and the steps I took) was that the little metal disc that is actually the 'switch' looks to get tarnished over time, and on one of them I saw there was a tiny spot of corrosion build up too - which was causing the connection to be intermittent.

So I'll start from the point where you've got the window switchpack out of the vehicle, on a bench - and the switch module removed from the trim and the board unclipped from this. On my one there were a bunch of Torx head screws holding the switch module to the trim. I think they were either a T10 or T15. I just grabbed the screwdriver off the shelf and didn't check what it was!

So, you've got this board in front of you, with a whole load of dust and crud on it, and a bunch of switches that don't work... The first step is to take the switch caps off. The one I was working on I could unclip them with my fingers but pulling up one side, and then following with the other. Technically you don't NEED to remove them, but I found it useful at the end to make sure everything was still sitting in place after the clear light pipe octopus was put back in place.

(the Rear Inhibit switch was my test one so was put back together and tested by this point!)

So next, turn the board upside down and you get a view of the bottom of the switches like this:

Take a sharp knife and then cut off the black plastic tips of the switch housings. Be careful removing them as you want to put them to one side for later... We'll use them to help hold the switches back on after the fixing is done.

You should end up with something looking a bit like this:

You should then be able to remove the switch from the board. Sometimes they need a bit of persuasion from a thin spudger (though I was able to pull most of mine off with a bit of a wiggle)

And you end up with this:

And the board looking like this:

Then take your sharp knife again (I use a scalpel for these smaller bits) and cut the tape around the switch pads so they can be removed:

Then remove the switch pads and you'll have a board that looks like this:

And then you get the switch pads separate. as you can see, there is some tarnishing on one side of these.

I then used a small screwdriver just to scratch the surface and scrub the tarnishing off of it.

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!

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:

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!

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 as well and used a pair of tweezers to flatten it out to make sure that it's not going to come apart again.

And you should end up with something like this:

And a whole board of them:

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.

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

No pictures?

Looks like Marty's personal server has died, so I've just edited the post to put them back.

Hmm, odd... The server is still running as I can access it via my VPN... I'll have to check the links as I did have to update the web server software awhile ago and it typically broke a few other things that had been working. I thought I had got them all sorted, but maybe not...

I copied the link locations from the other side as I couldn't access the pics on your server.

I'm impressed!, faced with stuff thats all plastic dots like that I wouldn't have attempted it but in essence it seems straightforward, if my windows evver give trouble I might just have a shufty.

Do you mind if I jump on this thread rather than start a new one....?

I am having issues (I think) with my window switch pack. Short story is I bought a Range Rover and the windows did work when I got it but they have since packed up. I have found a dodgy door outstation with some transistors that had blown apart so I have replaced that but still no joy.
So far I have been concentrating on the switch pack but have opened up the BECM for a look, no signs of water ingress in there.

I have....

Pulled the footwell kick panels off and disconnected all the plugs in there. No signs of anything amiss but gave everything a spray with some switch cleaner then used a silicone spray grease and plugged it all back together again.

Looked at the diagrams in RAVE and traced the cables from the switch pack connector to the BECM connector and buzzed them out with a digital multimeter. Good connection on the 3 signal cables. Checked the grounds, have a good ground at the switch pack and BECM, get 11ish volts at the light bulb connection when the lights are turned on and get 13v when the ignition is on for the power cable. All three signal cables seem to have around 5v on them when the ignition is on and the switch pack is unplugged.

I've connected a 12v power supply to the switch pack circuit board outside the vehicle. I get 5.3v on the output of the voltage regulator and then it gradually drops across the board as it passes through various resistors. I get 5v on the output of two of the signal cables and about 3v on the last signal cable. Pressing the buttons on the panel makes no change on the signal cables but then I'm only measuring voltage. Not sure if there is a hidden digital signal in there that I would need an oscilloscope to observe?

I have removed all the switches from the board but the contacts were very clean and I get a change in resistance on the various chip pins as I press the switches so they are working well.

I have drilled through and soldered in links to a number of the copper plated through holes or via's as some looked a bit corroded. I have bridged one dodgy looking track with a cable.

I have replaced the failed door outstation with a much better looking replacement.

Unfortunately, still no working windows. Not sure where to go from here. I didn't really want to spend between £80 and £100 for a replacement from eBay but maybe I will have too and see if that solves the problem?

Craig.

Rob had a similar problem a couple of months ago, see https://rangerovers.pub/topic/2300-switch-pack?page=1. Marty does refurbed ones (www.p38webshop.co.uk) but he is currently working in New Zealand so can't help a lot at the moment. As mentioned in Robs thread, I've got a switchpack that works fine except for the sunroof and one of the rear windows that needs to go back to Marty once he is back, so you can borrow that to see if it is the switchpack or something external. I suspect something external as it was working although it could have been damaged by whatever burnt out your door outstation.

Thanks Richard

Just had a read of Robs post and it does sound very similar. I've just been sitting down with the board again and testing things, continuity on the tracks and voltage when connected to the power supply. Still not seeing anything obvious with it.
Tempted now to just run a drill through all the through holes and solder in the wire links to eliminate that as a cause.

I'll persevere for a bit longer then I'm away from home next week but if I get nowhere and you don't mind posting your spare switch pack, it would be useful to see where my problem lies. I only need to open a window a bit then close it again to prove the point then pop it back in the post to you.

Cheers

Craig.

Just thought I'd post a conclusion to my window switch issues.

I have just got back from a week away in Devon and while there, thought I would have a look at the FaceBook market place and there, 8 miles from where I'm staying is someone selling a big box of P38 spare parts. There is a complete air compressor and valve block box, air flow meter, air cleaner box, new fuel filter, new oil filter, various light fittings, interior fittings, a good remote key and lots more besides but more importantly, a window switch panel was there.
He was asking £140 for the lot so I didn't argue, bought it and last night when I got back home, plugged the window panel in, tried it and all the windows and mirrors are working fine again.
I'll test the air compressor and if good, stick it on ebay and see if I can make most of money back on selling that.

At least I know the switch panel I have is in someway faulty even though it seems to give all the right indications under testing. If Marty is interested in taking a look at it I'm happy to send it to him as it will only be going in my spares box then likely in the bin a few years time.

Craig.

I have had several of these where the clip from the mounting screws has fallen into the unit and shorted out the 5volt regulator. Normally a blown regulated and / or a burned track