Lotus Elan

speedo stopped

PostPost by: daverubberduck » Sun Nov 04, 2018 5:28 pm

My speedo has recently stopped working. It doesn't always read zero, sometimes it shows a reading around 10, 20 or 30mph, other times it's at zero, but it is never responding to my actual speed. But the strange thing is that the odometer appears to be working. Is this telling me that the problem is inside the speedo? It's an early +2. Also I had the engine out recently, I don't know if that may have anything to do with it. Any thoughts?
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PostPost by: ericbushby » Sun Nov 04, 2018 7:27 pm

Dave, if the odometer is working correctly then it would appear that the problem is indeed in the speedo itself.
I would suspect dust or fluff between the alumlnlum disc which turns the pointer and its housing. The clearances there are quite tight. There is no mechanical link at this point, only magnetic induction.
It may be worth having a go at cleaning it very carefully.
Failing that it is a job for a specialist.
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PostPost by: nmauduit » Sun Nov 04, 2018 7:36 pm

daverubberduck wrote:My speedo has recently stopped working. It doesn't always read zero, sometimes it shows a reading around 10, 20 or 30mph, other times it's at zero, but it is never responding to my actual speed. But the strange thing is that the odometer appears to be working. Is this telling me that the problem is inside the speedo? It's an early +2. Also I had the engine out recently, I don't know if that may have anything to do with it. Any thoughts?


is the odometer fully working or just moving a bit (like when the speedo hand moves)? it may be that the cable end was not put back right when the engine was put back in, and rather than transmitting motion fully with the square end inside the square hole it only transmits some of it by friction...
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PostPost by: ericbushby » Sun Nov 04, 2018 7:45 pm

Good point, so first check the Odometer properly on a test run.
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PostPost by: daverubberduck » Sun Nov 04, 2018 9:26 pm

Thanks for both of those replies, it is very helpful. I should say that I did not remove the gearbox so did not touch the cable at all, but maybe it has moved with all the work so it is worth checking the odometer properly. If that is OK then I will attempt to clean inside the speedo.
thanks
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PostPost by: nmauduit » Sun Nov 04, 2018 9:33 pm

daverubberduck wrote:Thanks for both of those replies, it is very helpful. I should say that I did not remove the gearbox so did not touch the cable at all, but maybe it has moved with all the work so it is worth checking the odometer properly. If that is OK then I will attempt to clean inside the speedo.
thanks
Dave


well, if the cable has not been undone from either end it may have been kincked or broken inside during the engine removal : you may find out if the speedo end is still connected all the way to the crank by taking the speedo out and trying to turn the square with the fingers (it can flex some torsionnally, but not a lot).

good luck !
Last edited by nmauduit on Mon Nov 05, 2018 10:42 am, edited 1 time in total.
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PostPost by: nomad » Mon Nov 05, 2018 7:36 am

Once you remove the speedo so that access to the cable is easy you should be able to remove the inner cable with no difficulty. That will allow you to inspect the cable and to lubricate it if it is OK. They can break but definitely should be lubed every few years. I like to coil them up in a 5 gallon pail with a little engine oil over them and an overnight soak. That is after a good cleaning in solvent.

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PostPost by: daverubberduck » Mon Nov 05, 2018 9:44 am

I doubt if the cable has been lubricated in a very long time, so I will do this. Do I have to remove the actual gauge? Or do you mean just disconnect the cable from the gearbox? If I disconnect it from the gearbox, is it possible to pull the cable out without disconnecting it from the back of the gauge?
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PostPost by: nmauduit » Mon Nov 05, 2018 11:00 am

daverubberduck wrote:I doubt if the cable has been lubricated in a very long time, so I will do this. Do I have to remove the actual gauge? Or do you mean just disconnect the cable from the gearbox? If I disconnect it from the gearbox, is it possible to pull the cable out without disconnecting it from the back of the gauge?


It is not difficult to disconnect the cable from the gauge, so if you can also disconnect it from the gearbox (more of an access issue) you'll have options. What I would do first is disconnect it from the gauge and try to turn with the fingers the square end that was in the gauge, to assess if the cable still maintains a mechanical link all the way to the cranck (if you can do several turns it's loose : you'll have to find out it you can plug it back, by pushing while turning from the gauge end, and if it turned smoothly before being plugged back). You will notice then that the cable itself can move along within the flexible tube that holds it : the cable length is cut so that a square bit protrudes at each end of a length enabling to engage in the matching square hole when both attaching fittings are screwed in. If one end is pulled and not put back square in square, which can happen since the cable itself can move along, then a poor transmission of motion can result.
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PostPost by: daverubberduck » Mon Nov 05, 2018 12:58 pm

OK I got it, thanks for explaining it to me. I will give that a go in the next couple of days.
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PostPost by: daverubberduck » Mon Nov 05, 2018 3:24 pm

I managed to disconnect the cable from the gauge. The inner cable with square end does not turn, I can twist it a little bit in each direction but it won't turn any more than that, so it is definitely connected to the other end.
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PostPost by: alan.barker » Mon Nov 05, 2018 3:57 pm

Be very careful when cleaning the Speedo what liquid you use. Don't use any old Solvent or you will remove the Numbers on the Dial etc. Try cleaning with a very small Brush or Coton Buds.
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PostPost by: daverubberduck » Mon Nov 05, 2018 6:43 pm

Thanks Alan. Noted. I was hoping not to have to go inside the speedo, but if I do, is it easy to open up? I tried getting into a Smiths gauge once before (not a speedo) and found it very difficult without damaging it.
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PostPost by: RichC » Mon Nov 05, 2018 9:11 pm

pulled mine apart last summer . my speedo was always very inaccurate and jumped all over the place until one day it stated making the most incredible screaming noise, so much so that i had to stop driving .
The mechanics inside are very simple and i doubt you'll have much difficulty as long as you bend back the retaining tabs on the bezel very gently .
Once inside i found the worm drive gear just needed lubrication . The end result is a speedo in synch with all those speed awareness lights on the roadside.
When you have your speedo apart and in your hands try spinning the input shaft between thumb and forefinger to see the speedo needle rise up. You should feel & hear that it is smooth with no vibration before you reassemble :wink:
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PostPost by: daverubberduck » Tue Nov 06, 2018 10:37 am

Thanks Rich. I will give it a go.
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