TD5 auto XYZ stripdown

[ThreeSheds]

So... Occasionally I get the flashing M+S warning on the dash, which goes if turn the ignition off and rapidly move the stick through it's full movement a few times. Recently it has been getting worse to the point where i have to stop every few miles to sort it, so I thought I would have  look at the XYZ switch, which is well known to be the most likely culprit for this problem. Since a new one is upwards of £400  and a second hand one may be the same  condition as mine, I decided to have a look inside it

First - my car has a cat which means that I can't get to the XYZ switch without removing the J pipe... which means I need to remove the front cross-member which turned out to be a bit of  nightmare with four bolts shearing and two rounding off. The J pipe came off ok (surprise!), and after a struggle to get the change lever off (the one that sits outboard of the XYZ switch), I removed the XYZ switch it's self. That much is well documented elsewhere, so no pics of that, but now - lets have a look at the actual switch which, as we all know, looks like this:

Firstly I checked the condition of the plug, which has been known to cause trouble, but mine was like new:

In fact the whole switch looked pretty good:

And as you can see, it is held together with seven alloy rivets:

which need to be drilled out. Here was the first problem because as soon as I started to drill, they started spinning, leading to this mess:

Initially I was using a 6mm drill bit. After some experimentation and a lot more mess, I found that by using a 4mm bit at high speed, and by being really gentle - I was able to drill them out and open the case up:

What a surprise! I was expecting a gungy mess of corrosion, but again - it looked like new... This was troubling - if I could find nothing wrong then it's obviously going to be something rather more expensive  

A closer inspection of the underside of the rotor revealed that the 'heavy side looked ok (although one of the tangs was a little bit low - maybe 0.5mm - so I levered it up a bit) but that tracks that it operated on showed signs of corrosion or arcing perhaps... it's difficult to photograph, but look where the greenish pointer is. that's where the marks are:

The other side of the rotor showed definite signs of corrosion or arcing or something on one of the contacts but it's track was ok - see the fourth one from the left:

So, I cleaned everything up, removed the old grease, lightly cleaned the contacts with VERY fine emery (8000 I think), lubed it up and put it back together.

On the subject of cleaning, I have read somewhere that the contacts should not be cleaned because it will remove the plating. I reasoned that cleaning would be better than the oxidation and/or burned grease that was there and that if it only works for a while then I am no worse off when it next fails...

Also - on the subject of lubrication: It appeared to have some thin white grease applied originally, but after looking at my range of options I decided on a thin brush-application of ACF50. Hopefully nobody will throw their hands up in horror at this, but if they do then it won't be going back on the car until boxing day so speak now or forever hold your grease...

Now for the reassembly - well it's remarkably simple really - you just put it back together and screw it up with M4x16 Allen bolts and nyloc nuts. I used stainless ones and only did them up lightly since the original rivets were not that tight:

The screw heads do stand proud, but should clear ok. One of the nuts is a little tricky to hold but snipey pliers were enough for the gentle torque I was using:

After I had finished reassembling the switch I noticed a possible reason why it looked so clean - is that 170912 a manufactured date perhaps?

Anyway - next I am going to fill the corrugated wire protection with waterproof grease and then refit it.

If anyone is thinking of trying this, give it a go, it's not that hard. Oh and I found out that the cross member does not need to be removed since the (disconnected) J pipe can be slid far enough to gain access with it still in place.

Finally - I had to go out and buy some 4mm nuts and bolts, which come in bags of fifty - so if you are thinking of doing this, and if you are a supporting member, pm me and I will send you a set of seven nuts and bolts suitable for the job - I have enough spare for the first four applicants...

[Maverik]

Good luck... I hope it works...

[ThreeSheds]

Fitted and tested... working fine

Thats £440 + labour saved

[BogMonster]

Blimey, I'm sure they used to 'only' be about £100

Good writeup, maybe one for the tech archive @western ?

[Maverik]

Nice one, nothing beats a good clean and check over, the number of folk that have probably just thrown those units away and just replaced.

[western]

Link to this post added to the Gearbox section of our Tech Archive. 

[Ally V8]

They were £96+ Vat retail when I bought the first one many years ago,always been a DII pain.What Threesheds needs to do now is to id the feed wire to the reversing lights, cut it and put in a small relay to take the full 42W load away from the contacts in the WXYZ switch. I've done this on my own car and also do it on all the customers cars that come in with the same fault. I can't remember the wire colour or mutltiplug pin number,but you can access it at the bottom of the N/S A pillar. A feed for the relay  can be taken off the large feed wire to the heater blower at the front of the N/S footwell with an inline fuse for circuit protection.

I've done loads of them now,it seems to be a good upgrade,its always annoyed me that LR have jacked the price to 4 times the original,(Already expensive) level,but done nothing to upgrade the switch itself.