Sounds easy ....but it ain't, odometer fix

[K Simmonds]

I believe that's the connector for the ambient temp display...

I can recall using it for that on my NG Coupe and I've had a look behind the clocks on my 80 and it's there even on that car.

[SorenR]

If you know someone with a FDM or SLA 3D printer ...

https://www.thingiverse.com/thing:5150038

[Obli]

The black connector plug on the back of my 90 20v cluster is not plugged in to anything (I don't have an ambient temp display). On mine, it's held flush against the back - there's a couple of lugs to hold it, connector terminations facing up with body flat against back of cluster.

[Flying Frank]

Ah yes I spotted those but as you can imagine I was puzzling as to where it had come from as I disassembled everything about 3 weeks or more ago and my mind was blank as to where it had been attached. No temperature read out on mine either so it'll get clipped on the back when and if I ever sort this speedo issue out
Thanks guys for putting my mind at rest.

[Flying Frank]

Starting to lose the will to live....well not quite but having taken an assortment of instrument clusters in and out of my car as well as disassembling my original one about 4 times now. I have reached a conclusion which tractor Dave pointed out a while back.

My car has the 7A 5 cylinder engine ( 20V ) , it seems that this speedo unit is different to all other 5 cylinder Coupes and saloons . Speedo parts are not interchangeable and it seems the speedo part of the motor also drives the odometer.

I took the little motor out as described in MikeS2 article which Slacky posted up, and guess thats all I need plus of course a needle that will fit back into it but finding parts like that are not going to be easy.

I started with an odometer problem caused by the disintegrating miniature plastic cog , but created another problem when I removed the speedo needle and damaged the pin that the needle is attached to.

I suppose another option is to ask tractor Dave to have a look at it/fix it but he sounds rather busy at the moment. Taking the dash in and out of the car every time to see if my "meddling" has fixed the problem becomes rather tedious in the end .....and that's putting it mildly. Still, I guess you'll all be telling me that's the fun of owning these old classics...... yeah right

[Obli]

I know the feeling, Frank. It's been a nightmare with the needle breaking but don't give up now, though! I've had the instrument cluster out God knows how many times now, but it gets easier. A lot of the jobs haven't been straightforward. I've got to take the cluster out again to replace the voltage regulator and LCD clock (for a third or fourth time now). I was thinking I might ask you - you must be able to do it with your eyes closed by now Psychologically, I can't be bothered, but I will. It'll be worth it in the end. Perseverance will pay off. That's all I've had at times

I'm sure someone here will be able to help you out with the required bits. Don't despair! It's one of the joys of having an old car (I had to say it!)

[Flying Frank]

Hi Obli, thanks for the positive words of encouragement. Incidentally , if you need that voltage regulator, I can send you one as I now have a couple of instrument clusters in various states of dis-array. In fact I swapped the two smaller gauges ( fuel and water temperature ) into my car as the later ones are marked with values as opposed to just a heavier white line . Would also like to change the LCD clock but am flinching at that slightly in view of my past successes with the speedometer/odometer.

[Obli]

Thanks for the offer Frank. I've acquired a vintage regulator from Dave and it's sat there (waiting for me to pull my finger out).

The LCD clock replacement procedure isn't too bad. Stopped instructions were good. Rev counter needle has to come off (!), dial face, a plastic piece and a few screws behind. I think the main thing is cleanliness and noting the assembly order. Circuitry contacts, conductive pad(s) and LCD clock itself must be pristine. There are also two versions of the LCD clock. v1 and v2, as partworks.de reference them. If you're going to order one, I'd check on their site and identify which one you've got first. I think you can do this by lifting the dial face and having a look underneath. That's what I did, rather than take it all apart.

Having said all that, my new clock from them still has a couple of missing segments. They were good enough to try and help me fix it then decided to send me another new one free of charge to try. That's something else I need to get done!

[Flying Frank]

Well!!! I think , repeat THINK, I can put this post to bed now.

A while back I was offered a speedo cluster from a chap who lives only about 4 miles away ( as the seagull flies) but in actual fact is the far side of Falmouth Bay from where I am so actually almost an hours drive away. I had procured some parts from him before, off an Audi Coupe B3 he was breaking ( having been unable to find a buyer for the complete car )

I cut a small rear wing section out of his to enable a repair on my car and at the time he had offered me a speedo he had in amongst a lot of other spares he had accumulated over a 10 year period. I thought back then I could sort my cars problem with fitting the cogged drive wheel but as has already been explained I screwed up removing the speedo needle and ended up with nowt,

So for a mere £20 I bought his very high mileage ( 224K ) speedo having been assured it all worked ok when removed from the donor car some years earlier.

Full of hope, about a few months back I fitted it and drove off on the test run......speedo was flicking around like mad and the trip meter was reading a bit then stopping and all in all not good. So I went back to my old speedo and put the bargain £20 to one side. Later however, with a dial in front of me with no needle on it decided that maybe a flicking needle was better than nothing at all so once again out came the original unit and in went the 20 pounder.

Subsequently on the occasional drives I did in the car it seemed that the needle was flicking around at almost the correct speeds and just occasionally the odometer would read a couple of miles. I fixed in my Garmin GPS and realised that the top of the flick was the correct speed momentarily and the flicks were only incorrect by possibly 3-4mph at the lower end of a flick. So that encouraged me to keep the unit and then I did a longish journey ( for me anyway , about 20 miles ) and on that journey the needle had steadied down almost completely , and the odometer had clicked up a decent amount of miles too.... On the return journey , the odometer read correctly and the needle was as good as you could hope for.

In conclusion I can only assume that the prolonged storage of the unit had seized the workings up and with keeping the car dry and warm and using it only gently now and then, the whole thing had freed itself off .

The cars correct mileage was about 180 K , and so it has now jumped to the 224K figure, but I'll live with that as it really is so good to have a correct working dash....only slight issue is the lights seem a bit dull at night so may have to consider changing all the bulbs or maybe the rheostat just needs a good clean.

So just to say thanks to all who offered help and advice over the past few months , all much appreciated.

[Hanuman]

Electrical/electronic, I’d say. It might settle down. It may occasionally play up. Drive by ear, and experience, and set this all aside for a late spring revisit.

Most of these systems are reliant on electronic senders and signal cables, these days. Long term storage of anything electrical can lead to simple tarnishing of connections. Automotive circuit boards are of a pretty low level of integrity by comparison with the electronics in black boxes that you and I are more accustomed too. Thus reliability is lower. And nothing electronic likes being shut down and unsympathetically stored for any period of time.

Even the famed quattro has a small stepper motor involved, and a circuit that occasionally goes faulty, and burns out entirely one of the more expensive components- the digi dash.
Faults with the odometer can easily be the gearbox sender, it’s local connection. The connection at the instrument cluster. Solder dry joints where components and interconnects… connect. An erratic signal to the chip that drives the stepper motor that advances the gear. Or disturb the line resistances. Some of the same signal sources that result in static, or erratic needle behaviour.