G/box: 850 Auto: PNP Switch Cleaning

[warthog]

Hi Guys and Gals,

Long time no post..

For the last couple of years the PNP switch has been dodgy. Reversing lights not always coming on when selecting reverse gear, that sort of thing. Recently first thing in the morning the Orange trans light would flash momentarily on putting into drive. These I could live with, (std gearlever cycling fixed it for a short while), but in the last 2 days 3-1-3 error codes set with trans in 'limp home mode'. OK when warmed up, but still a pain.

Time to do something about it preferably before I drive to Switzerland in the next month.

So, 'bull by the horns', 'nothing ventured nothing gained' and all other similar homilies I decided to take the PNP switch apart and clean it. Can't be too difficult now can it?

I think someone posted some time ago on cleaning the switch, but I couldn't find it this morning.

Hour and a half later, all done, back together and works a treat.

Basically I followed the steps in Bay 13 (http://www.volvospeed.com/volvo_performance.php) to remove the switch. Mark the position of the outer selector cable clamp with a scribe around the nut heads before loosening the clamp. Once this clamp is removed, use a straight edge against the studs and scribe a line in the top casing of the PNP switch. This will ensure that you replace it in the same place.

Once the switch is out of the car gently clamp switch in a vice. Switch halves are held together with 6 small cross head bolts. Position switch with Al casing on the bottom and you won't loose the 3 springs and contacts from the moving arm when you lift the plastic contact housing off. They aren't so spring loaded that they will spring out when you lift off the top (unless they are stuck I suppose). You will have to prise off the steel shroud where the cables exit the switch as this ties both halves together. There should be enough slack in the wires to do this without bending the shroud too much.

To clean the contacts and tracks I used a small oil stone and some WD40. The tracks are flush with the plastic holder so you can gently rub the oil stone over the whole face to even up any wear tracks. There is a rubber 'o' ring sealing the joint between the two halves, On mine this was stuck to the plastic half and I didn't realise that it wasn't a moulded feature until it fell away. This makes cleaning the contacts very much easier if you remove it first. I used brake cleaner to degrease and clean everything before smearing the contacts, springs, arm and tracks with some general LM grease and re-assembling.

Re-assembly is the reverse of the dis-assembly taking care to line up the switch with the previously scribed line. DON't overtighten the 13mm nut on the selector arm.

Time will tell if I've saved myself £100 or so by not buying a new PNP switch, but the contacts now look like new so we should be good for another 140k miles I hope.

Cheers

[Mike Smith]

When I did mine, I couldn't have got it sitting as it was previously and therefore cannot start the car when it's in neutral only in park, might get around to adjusting it someday! I seem to remember Chris posting up a method of adjsuting a good time ago?
Nice write up Brian, have a save journey in those hills!

[Jod T5]

it is a long time brian, did you by any chance take any pics so we could have our own volvoforums version......rich kelly rocks btw......
cheers
jod

[warthog]

Hi Jod,

I do it every time... so eager to get the job done that it's only when I finish that I think I should have taken some photos - sorry!

If someone has an old PNP switch they could pop in the post I'll take it apart and do some pics of the process though.

Cheers

[Madleee]

Please someone follow this up.

atm I'm at the stage of reverse lights not working and the odd G/box limbo when using the shift to aid braking (I swear Trinity Hill in Barry is a 1 in 2!)

I would contemplate a contact clean.

I realise I'm talking myself into this job now so I'll shut up! LOL

[Mike Smith]

Have you checked the fluid levels?