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88 110 rear wiper switch - anyone repair one of these?

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The rear wiper on my 88 110 stopped working a while back, so yesterday I started tracking it down. The motor works, and I have 12v to the solid green wires at the switch and at the motor. The problem appears to be a bad switch. This is the old style round knob rotary switch with push-in for sprayer. The sprayer push function does operate the pump, and I do have 12v supply at the back of the switch. I cannot get 12v to the red/green wire though which should feed the motor when switch is rotated to "on" position. If I put a jumper between the green wire (12v from fuse box) and the red/green wire the wiper motor operates. I do have 12v at the brown/green wire which is the park function power feed. This should only have power if the wiper is not parked (assuming the park switch in the wiper gear box works). In any case I don't think is important - if I need to park the wiper manually no worries. So I just need to get 12V to the red/green wire which the switch apparently refuses to do.

The big problem is they want $250 for a new switch over here in the US! Has anyone opened one of these old switches and tried a repair? Any "user servicable parts" inside? I guess I could always just fit a basic flip switch in the dash to operate the wiper and a push button for the sprayer and ignore the park.

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They probably aren't that complex inside being of Lucas origin, but all the bits will probably fall out on disassembly and it may be difficult to work out how to put it back together. Do able if you have the patience.

They should be available new here in the UK, so email suppliers to see if they will ship to the US. Or search Ebay.co.uk (not .com) and see if there is anyone in the UK selling them willing to post to you.

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Thanks for the replies - FIXED it myself. (See pics) It can be opened by bending the 3 metal tabs. Best to keep the metal side down, or you will lose the 2 spring-loaded ball bearings that set the switch detents. Very simple as predicted. Rotating circuit board connects red/green wire to green wire (12v from fuse box when ignition on) when switch is on (rotated clockwise 1 click). The same circuit board connects the other contact, brown/green wire, to the green when the switch is off. This is what parks the wiper.

The problem with mine as you can probably see is the contact for the red/green wire was burnt, not to mention no longer touching the circuit board. Apparently it had been quite hot and melted the plastic switch casing at the base of the contact (similar to what can happen inside of the headlight dimmer switch). Not only had it shifted so that the contact no longer hit the board, but it also managed to break the continuity between the wiper contact and the spade connector for the red/green wire (they are riveted together). So even though I expected carefully bending and cleaning the wiper contact would fix it, I had to re-establish continuity to the spade connector/rivet with a blob of solder. Moral: always check continuity with a meter!

Seems someone had installed a 20A fuse in the circuit where a 5A should've been. So that partially explains the heat/melting (vs blowing the fuse). I suspect the contact started arcing and blowing the fuse and some PO's solution was a bigger fuse. Wiper motor seems to work just fine w/ 5A fuse in place now. Not sure what happens if the wiper is frozen to the screen when you turn it on.

Inside of defender rear wiper switch

Rotating circuit board inside Defender rear wiper switch

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I think what causes the plastic to melt is when the contacts get dirty. A dirty contact (or poor pressure on the contact) causes resistance which makes the contact heat up and eventually melts the plastic.

I remember a deep fat fryer my parents had where the mains plug would get so hot you couldn't touch it, that was caused by the fuse being loose.

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