Speedo needle swinging wildly

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KeithL
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Speedo needle swinging wildly

Post by KeithL »

We took the Traveller out today and had gone about 2-3 miles when we noticed a slight rattling noise from the dashboard. My first thought was something in the driver's glovebox but we then noticed that the speedo needle was swinging around about +/- 10mph from our true speed. We thought about what to do for a few minutes during which time Jayne had to slow down and change gear. When we speeded up again and changed back into 4th the rattle had gone and the speedo needle was behaving normally. It was fine for the rest of the journey, and all the return journey - about 18 miles in total.

Any thoughts as to what could be going on?

Boomlander
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Re: Speedo needle swinging wildly

Post by Boomlander »

Sometimes the inner wire of the speedo cable binds up on the outer casing and then frees itself causing the needle to fluctuate up and down.
This is probably what you can hear as a rattle.
I had the same problem with my old series 2 and I replaced the cable with a new one which cured the problem. :D

don58van
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Re: Speedo needle swinging wildly

Post by don58van »

I agree with Boomlander's diagnosis.

You could start by releasing the speedo from the dash and checking that the cable connection is properly screwed to the back of the speedo. While there, you could try putting a very modest amount of oil the the end of the cable. The amount must be kept small to avoid the inner cable lifting the oil into the back of the speedo mechanism.

There is another possible (less likely) cause: Sometimes the odometer mechanism can jam , which will cause the speed part of the mechanism to fluctuate. This requires the speedo to be opened up and serviced.

Don
KeithL
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Re: Speedo needle swinging wildly

Post by KeithL »

Thank you both. I'll take a look. You loosen the two screws accessed through the gloveboxes if I remember right. What oil should I use on the cable - a dab of engine oil or something lighter? Anything else to check for whilst I have it out?

I meant to say, the odo seemed to be working fine throughout all this, gently scrolling round at a steady rate. We were doing about 40 mph at the time.

don58van
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Re: Speedo needle swinging wildly

Post by don58van »

I think engine oil should be OK. It would be good if you could wait for at least a few hours after oiling --or preferably overnight--before reassembling and driving and to allow the oil to creep down the cable.
While the speedo is out and drive cable off, you could also check for excessive friction in the mechanism by using a suitable object to spin (anti-clockwise) the input. It has a square hole into which the inner cable fits. A small straight-bladed screw driver may do the job. There should be no more than slight resistance to turning.
Of course, throughout the process, it is important not to unduly disturb all the wiring on the back of the speedo.

Don
KeithL
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Re: Speedo needle swinging wildly

Post by KeithL »

I have finally got around to looking at this but fell at the first fence in that I could not get the screwdriver into the screw heads to loosen them. If I use a torch and a mirror I can see the screws (both Phillips), and I have a spare speedo so I know exactly where the screws are, what size screwdriver to use, and how far in the screwdriver needs to go. Is there some trick of the trade I am missing or is it just a matter of making myself comfortable and keeping trying?

simmitc
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Re: Speedo needle swinging wildly

Post by simmitc »

It is just a question of perseverance. Use a medium sized head crosshead driver, about six inches long. Keep the shaft horizontal and insert into the hole and then feel the point home, maybe an inch from the side of the glovebox. If you get really stuck, then remove the glovebox liner on one side to reach the screw on the speedo. Having done one side, you'll probably be able to reach the other side through the hole. NB loosen the screw in the speedo, do not remove it.
KeithL
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Re: Speedo needle swinging wildly

Post by KeithL »

Thanks for your guidance @simmitc - I managed to loosen both screws without too much trouble today. Maybe I was just tired yesterday.

The next problem I have hit is that the speedo cable is too short to pull the speedo out enough to unscrew it. I may be able to loosen the various clamps and slide it along a bit to get some extra length but failing that it may be easier to disconnect it from the gearbox end.

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