Speedo suddenly now inaccurate

[Ads1987]

So my 1.7 diesels speedo has now decided to be around 20mph out, apparently I'm doing 30 mph on the motorway when keeping up with other traffic. It's been fine before and randomly started wobbling over a range of 10mph, so for example it reads anywhere between 30 to 40mph when I'm doing over 50mph.

I took the cluster off and disconnected the speedo cable but no difference, has anyone had this prob or know a likely cause? I looked on the wiki and forum search but couldn't seem to find anything?

Thanks for your help,

Adam.

[CovKid]

Check where the cable exits front wheel (in the centre). If the square hole is almost rounded, or the e-clip missing) you'll get pathetic/inermittent/fluctuating readings. The same could be true if the cable is damaged. Otherwise it could be the cogs in the speedo missing a beat.

[ghost123uk]

Check where the cable exits front wheel (in the centre). If the square hole is almost rounded, or the e-clip missing) you'll get pathetic/inermittent/fluctuating readings.

I have to sort this on mine, it is as Ralph says, the square hole in the grease cap in the centre of the nearside wheel is rounded. Don't think it can be repaired so need to source a new grease cap. I will be near a VW van dealer later today so will enquire if they can supply one. (not saying you need one, but it is a distinct possibility).

[ghost123uk]

p.s. = £15.70 + P&P from VWHeritage here

[CovKid]

You can repair it (at least for some time) by working the inside of the cap with a cold chisel to close the hole and then file the hole square again. I used to do that when the prob occured on Beetles and they seemed to last ok.

[Oldiebut goodie]

Weld the hole up, drill pilot hole and then square off with a needle file. Easy peasey.

[CovKid]

You just have to watch you don't increase the thickness too much with any weld (particularly true on the inside where you can't grind it off)

Does work though - done it that way too.

I must admit, I've never replaced a cap except once where it was such a poor/loose fit on the hub, a replacement was the only option. That was second-hand at that. Never bought a new one in 25 years.

[Ads1987]

So is that like a dust cover fitted at the hub on the n/s/f behind the wheel I assume? I didn't know where the other end of the cable took the reading from, that's great thanks guys I will look at this

[kit]

My mechanic just welded the cable end to the cap worked well until he had to remove the cap, idiot.

[Oldiebut goodie]