PNP replace or clean?

Post by **precopster** » 10 Jan 2012, 02:02

I took my wife's PNP out in her 850 tonight, well except for splitting the wiring connector at the large connector (something I would have to do if I were to replace it) so I'll dismantle it tomorrow night and clean it.

I couldn't see a way past removing the alignment pins in the connector so I could split it and fit the new one I bought.

I was able to measure that pin 1 & 2 are the contacts for the reverse position so I'm going to use this as my calibration point.
Does this sound like good reasoning? I've marked the body where the bolts attach it to the gearbox so hopefully it's just PLUG and PRAY

Post by **precopster** » 12 Jan 2012, 03:03

So I couldn't ever find a way to split the factory connector from the PNP portion of the connector so I could fit the new Scantech one I bought. I tried pulling with pliers until I turned blue in the face then my hand slipped and wacked itself into something

What I DID manage to do is CLEAN the old PNP switch very carefully, retension the springs in the sweeping arm by stretching them a little and file the three small copper contacts flat again. I used Carby cleaner & my toothbrush to clean the baked on hardened grease from the large sweeping copper contacts.

I think the pics below spell the story out.

BTW I took apart the Scantech PNP I had purchased for this job just to see how it works prior to doing all this & I can say it's an exact copy of the factory switch right down to the brass arm shim, the copper contacts, the casing, the connector & numbering and the rubber seal around the casing. It wouldn't surprise me at all if Scantech are buying them from the same company that provides them to Volvo.

After the clean the car started and the reversing lights came on first time. It also starts in neutral every time, which was a problem before. Have to test drive it later.

EDIT: After finally finding the excellent PNP write-up on this site (https://www.matthewsvolvosite.com/forums ... =1&t=29930) I found the error of my ways. I should have released the connector apart by prying on the small blue tab at the end of the connector. I did the PNP clean in the engine bay which I wouldn't recommend if you hadn't previously had one apart before....too many small parts can drop in the engine bay.

Post by **erikv11** » 12 Jan 2012, 09:07

Hey that is really useful info about the Scantech switch - I am so suspect of everything they sell, it is worth noting when a particular item they sell appears to be good quality.

So why the Vick's, is it just what you had around that is petroleum-based?

Post by **rspi** » 12 Jan 2012, 09:41

I would say replace or rebuild the switch. If you clean it, I'd use some fine sand paper to make sure it's clean. Just an akward job to redo in 3 months.

NewToVolvo850s · Post by **NewToVolvo850s** » 12 Jan 2012, 10:48

Well today it finally went out. When its in drive it revs up for like 3 seconds and then the wheels catch and it spins tires. It also does it in reverse. My local shop said they'll replace it for $90(parts, tax labor)

Post by **jblackburn** » 12 Jan 2012, 11:36

-No reverse lights
-Cant go over half throttle
-Shifts weird
-Dash lights shut off when I go into drive

Did it fix any of these issues?

The revving up and then smashing into gear is a line pressure problem, however - not the switch.

NewToVolvo850s · Post by **NewToVolvo850s** » 12 Jan 2012, 11:42

Oh ok, and I havent had it replaced yet in 2 hours I am taking it into the shop. $90 seems really, really cheap though to replace it.

Jow could I fix the line pressure issue?

Post by **jblackburn** » 12 Jan 2012, 11:44

Either there's really, really, really nasty brown and burnt fluid in there, or that transmission is in its death throes.

Your issues at the beginning of the topic are a separate issue (likely the PNP switch as everyone suggested), but the 2nd symptoms aren't good.

NewToVolvo850s · Post by **NewToVolvo850s** » 12 Jan 2012, 11:47

how can i fix the fluid? thats what i think it is, the problem started this morning.

Post by **jblackburn** » 12 Jan 2012, 11:54

A transmission flush (specify that they absolutely need to keep it AWAY from a flush machine.)

The best thing to do would be to dump the contents of the transmission pan through the plug to get out any settled crud, and then flush another 9 qts or so through the radiator cooler hoses.

You can show them this if they're not used to working on Volvos:
https://www.matthewsvolvosite.com/forums ... php?t=8767

Take out the transmission dipstick (it's yellow and kinda hidden by the battery) and wipe it on a paper towel. If the fluid is not a bright, clear red, the flush is worth a shot.

Mine looked like this when I first got the car:

PNP replace or clean?

Re: PNP replace or clean?