Anything and everything Spitfire.

Hi all, on my way home from Manchester my Speedo exhibited sporadic speed readings and then eventually failed completely. I have a Spitfire 1500. The Speedo cable is new (as of 3 months ago). I suppose my question is - what's failed?

The speedo worked then stopped registering then worked again on a number of occasions. This would suggest that the cable is connected at both ends and is turning although I have yet to prove by driving along with the cable from the back of the speedo to ensure that the cable is connected at the gearbox end and is turning. Once the gearbox end can be ruled out and the speedo end seems to be OK, how can I ensure that the speedo end is driving the internals of the speedo and that there is something intermittent in the speedo?

The speedo now seems to have failed completely. I know I can get a new one or get this one repaired but I was wondering whether anybody has had such an experience and can tell me what is the most likely point of failure. I will probably be removing the speedo to check the cable and that there are no kinks preventing it from turning or causing too much resistance to turning. I would have thought that if the cable could not turn then the speedo cable ends would have been stripped or worn away so once stopped thhen I would not have got any readings again. Ho-hum.

I may resort to taking it apart and having a good look to identify whether there is anything obvious within the mechanism. I can always get a replacement or get this one repaired I was just lloking to see if anybody had any pearls of wisdom.

many thanks in advance and regards, Neil

I've experienced this many years ago and it was a faulty cable. I wasn't too sure at the time but I think the cable snapped and the rough edge that was left was sometimes enough to grip the other half of the cable to make it function but only very erratically

Thanks Steve, that makes sense to me. I hoped it was something simple and just want to get it working. If it is indeed the cable then so be it. It's only a few pounds worth. I don't suppose I'll get my money back on the faulty one. It wasn't a particularly nice job changing it last time but it seemed to be fine for a while until the other day. I'll wait and see on Wednesday when I have the day off. If the speedo end is not turning then a new cable it will be! I cannot imagine that the gerabox end is sometimes turing and sometimes not.

Thanks and regards, Neil

I've not know it happen on our cars, but it's not impossible for drive gears in the gearbox to wear out.
More likely if it's not the cable that's broken, is the square ends of the cable not fully engaging at either gearbox or speedo end (speedo end more likely) and perhaps the edge of the square hole has become rounded.
Has the odometer (mileage counter) stopped working as well? If not, then the problem will be within the speedo head.

You should be able to break this down and find which bit is faulty. If you can remove speedo, put a small screwdriver in the drive hole and turn sharply. You should get some response (in one direction). End of speedo cable should turn if you jack up car and turn rear wheel. If it's easier to disconnect speedo cable from gearbox then do this and turn cable there to check speedo and cable together. Gradually break down into bits until you find the faulty one. If everything seems OK it's down to how the bits fit together. Is everything screwed on enough?
Van

Thanks for your collective words of wisdom on this. I plan to look at this tomorrow and narrow down what has failed. I guess I will start at the speedo end and check that the speedo itself is operational by doing as Van suggests and giving the driven part a sharp turn. I imagine that the speedo works or it has an intermittent fault. I will check in addition that the cable driving the speedo is turning with thw wheels. If so then it must either be poor location of the cable onto the speedo, the cable end is rounded or the speedo itself. I found it a little difficult to believe that the cable was being intermittently driven by the gearbox but I supose that the angle drive thingy is worn and works on occasions.

Once again thanks for your pointers. I will let you know what I find out.

Croos fingers time that the cable is just not pushed home properly home and needs reseating!

Cheers, Neil

Apparently these guys are good if you need a speedo repair:

http://www.jdo1.com/Speedometers.html

I was thinking of sending my speedo there as the needle waves about or sticks in one position. It's not the cable as I have replaced that bit already

The saga continues! I did some investigating yesterday and found that the drive from the gearbox is fine and the cable was seated correctly. The speedo itself operates fine with a screwdriver is the rear and works fine when the speedo cable is pushed onto the drive mounting at the back. I can drive for a few metres/a few hundred metres and then the speedo fails to read at all. I am pretty sure that it si the mating of the cable to the speedo. I have removed the cable and checked that the inner is rotating and it is so it lloks like a new cable and if this fails to mate with speedo drive then I will need a new speedo or at least the bit of the speedo that mates with the cable if this is worn. I imagine that if it is plastic then it may have worn.

I'll get a replacement cable first and see if that sorts the problem. Ho hum, looks like I'll be scrabbling around under the car at the weekend changing the cable again!

Cheers, Neil

Problem solved! The problem was the speedo drive itslef was worn. The cable was intermittently mating/slipping where it should meet the speedo drive which seems to be made of plastic. I had several goes at re-seating the cable with the same result. I thought I was going to have to resort to a new speedo but was reluctant to shell out a few pounds for one off Ebay (etc). I also thought that I might be able to canibalise the worn part from a speedo but still required purchasing a spare. Then I decided to use a small rubber sleeve over the end of the cable. I found some 3mm sleeving from days when I used to install telemetry equipment and pushed that over the end of the speedo cable and voila! - a working speedo. I think the bodge should be fine as the rubber sleeve just fills the void where the previous cable has worn away the speedo drive thingummybob.

The job seems to be a good 'un.

Thought this might help others in a no speed indicated situation if nothing else seems to work. Maybe I am the only one who has experienced this but I prefered the thought of keeping the original speedo and didn't like the hastle of stripping down this and another speedo to sort it out. I may resort to that in the future but fingers crossed everything in my garden is rosy!

Cheers, Neil

Section : Dashboard and Instruments

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