Mk3 Speedo & Odometer

SteveLS400 · January 11, 2015

I've had the baby for years but these past few years I have been too unwell to involve myself with her. Despite her age she cost £20 to get through her last MOT and there aren't many 19 year old cars you can say that about. Anyway, I'm now trying to get rid of a few niggles. Hopefully the first of these has been resolved by having a new piece welded in the exhaust.

For sometime now the speedo has stopped working except on rare occasions. I use satnav for keeping to the speed limit. The really annoying part is no speed means no cruise control. In addition, the odometer also stopped working at the same time. About 3 years ago, the garage I was using managed to zero the odometer whilst trying to get the immobiiser off having disconnected the Battery and not followed my instruction to contact me which they still had to do. Nevertheless the odometer continued to work albeit from zero. The rev counter has worked throughout.

I recently had the entire display out to check all connections and to ensure that the speedo was not stuck. I reassembled the unit and was pleased that the speedo and odometer worked as did the temperature gauge which hadn't done so for years. All good? Er, no.

After a week it all packed-in again except Christmas week when all but the temp worked. For one journey. I'm told by my exhaust man that nothing appears to be missing/disconnected from the gearbox from which I am assuming the speedo is driven.

Given that I have disabilities and my income is severely limited, are there any fixes that I could do/have done?

I really would be grateful.

Malc · January 11, 2015

I wish I could help, but sadly I haven't a clue how to resolve the issue you have BUT certain someone will be along soon to advise...................

It's not just the needles sticking is it ? Mine sometimes does that and a slight tap resolves it all or it just springs back into go-mode after a mile or two.

Presuming the dash lights up ok ?

By the way, you probably now have the lowest mileage Mk3 ever !!! well done, just keep it forever won't you ???

Malc

SteveLS400 · January 11, 2015

I wish I could help, but sadly I haven't a clue how to resolve the issue you have BUT certain someone will be along soon to advise...................

It's not just the needles sticking is it ? Mine sometimes does that and a slight tap resolves it all or it just springs back into go-mode after a mile or two.

Presuming the dash lights up ok ?

By the way, you probably now have the lowest mileage Mk3 ever !!! well done, just keep it forever won't you ???

Malc

Hi Malc

The reason I took the dash out was to check the free movement of the needles. They were fine.

Its a pity mileages are noted on the MOT computer, otherwise you would be spot-on :hocus-pokus:

cleverdick · January 14, 2015

Not sure if it's any help, but I have the 1991 book (it could well be very different from the Mk3).

OK, so (according to the diagram I have) the cluster appears to be fed, in part, from the gauge fuse. If the fuse had blown/had intermittent contacts then I would expect none of the cluster to work. Interestingly, it shows the trip meter circuit (as opposed to the odo circuit) fed from the dome fuse!

The only parts common to the odo and speedo are the speed sensor (on the transmission, just above the crossmember) and the odo drive circuit (on the cluster). The various gauges are fed from an "11V Power Source" which I take to be a bit of on-board regulation. I guess you could check the distribution from there (fractured joints etc.)

Seems odd to lose speedo/odo one day and temp the next. I suppose at least you could (or get someone to) unbolt the speed sensor and test it independently, just to see what it's doing. Reading between the lines it seems to be an optical wheel/phototransistor kind of setup.

Mind you, it's not really the weather to be out there taking the car apart, is it? (Unless you have a centrally-heated double garage that is!) The winters I spent fixing my Cortina in blizzard conditions... I sure don't miss that!

PM me if you need specific info, bearing in mind that the combination meter section of the book runs to over 70 pages, and it may all be different in any case. I think a substitute cluster could be the way to go.

Somebody needs to make a test rig for them. A huge undertaking, but it could pay off...