Inaccurate B20F tacho reading

[sarumboy]

About 6 months ago, the tacho on my 95 2.0 auto 440 started to play up - not reading at all sometimes which I put down to dampness or condensation. But the problem has got worse, now there is a reading there all the time but its about a quarter or a third of what it should be. Can anyone suggest what's going on? Is it a connection issue or can the tacho generator fail? Where is it by the way, is the connector on the engine block somewhere? Thanks fellas.

[captainslow]

Give the dash a thwack and see if the reading changes-it works in temporary measures on the 480, although I assume you dont have an infocentre and thats the main problem zone!

[Clan]

sometimes the face of the speedo or tacho peels and a piece of paper like substance makes contact with the needle ...

[sarumboy]

Thanks for your replies guys. I've checked the instrument face and don't think it's peeling, doesn't seem to be a mechanical stoppage. And I thumped the dash loads of times on a 5 mile journey last night and that didn't work. On the way there, it didn't register at all and on the way back it read about half what it should have done. Mystery!
By the way, there is an Info Centre which is working perfectly.

[Alan C30]

There are a pair of multi plugs on the rear of inst binnacle which are JUST long enough to reach the gubbins when whole lot removed and VERY tight to reach when in situ, it might have 'just worked' loose. My 480 suffers bouts of this and I can just reach it when lying upsid edown under steering wheel, plug nearest door ( assuming RHD) is the one that has info panel on, from what I remember.

Cheers Alan

[sarumboy]

Thanks for that Alan. I've had a good grope up under the dash (wishing that I had smaller hands!) and so far the results are slightly better. Now the needle indicates correctly or not ar all and thats an improvement. Maybe I should settle for that. Cheers for the replies.
Sarumboy

[B20F]

If I understand correctly, there's a infocentre installed by a PO? In that case take a look at these (18) soldering points on the PCB. These come from the connector on the backside of the PCB. A failing or intermittent working speedo can be caused by cracked and/or dried out solder. I took a small 25w soldering iron and heated them one by one till melting point. I forgot which 2 are from the speedo, but to be sure I did them all. This cured the intermittent speedo in my 480.
Maybe it''s a good idea to replace all the dashbulbs when your at it!

[sarumboy]

Thank you, thats a brilliant suggestion, sounds very feasible to me and I'm going to tackle it. I couldn't believe it was the tacho gen itself as all other functions are OK, it has to be a bad joint somewhere in the instrument line. By the way, whats a PO in this instance? Thanks again, Sarumboy

[B20F]

PO= Previous Owner. The infocentre on the 440/460 was original only available in the turbo models. In the 480 it was standard, except in the basic 480S model. At least here in Holland that is, maybe different marketing policy from Volvo in the UK? I own a '92 480S but I installed an infocentre myself, together with aircon, cruise control, half leather seats, upgraded (green dipstick) B20F engine from a '95 etc. I could get a totalled (rearended) 480GT cheap, so now it's a full option 480S.