Speedo issue. Spitfire mk3

[Linda Carr]

Our speedo is playing up, odometer still working but the needle does its own thing, goes up and up, sticks at a speed then drops!! Anyone know someone to recondition her? Or should I look for a replacement? 

[glang]

Theres certainly companies to recondition them but its cheaper to buy secondhand on eBay although of course you get no guarantee that way. You do have to get the right one for your axle ratio....

[standardthread]

1 hour ago, glang said:

 You do have to get the right one for your axle ratio....

There is a way to check on the speedo dial itself, it relates to a series of small numbers that are printed/written on the dial face, I think from memory, at the bottom of the dial but on my Dolomite they are under the trip miles indicator. It's basically a part number.

Also check that the drive cable is sound and secure with no snags along its length, it could just simply need the cable very lightly oiling with thin oil.

Edited June 7, 2023 by standardthread

[glang]

Youre right although its the turns per mile of the speedo. You need the right one to match the diff ratio so for example 1152 turns of the cable needed to increase 1 mile on the mileometer reading. However just cos a speedo has the right TPM doesnt mean its the same facia as the original.

As for the cable I wouldnt have thought it could cause the needle to stick up as is happening. Theres an air gap inside the speedo between a spinning magnet driven by the cable and the needle so the latter should always be able to return to zero....

[standardthread]

10 hours ago, Linda Carr said:

Our speedo is playing up, odometer still working but the needle does its own thing, goes up and up, sticks at a speed then drops!! Anyone know someone to recondition her? Or should I look for a replacement? 

Has someone had the speedo apart?

Our Standard 10 box needed stripping and cleaning due to age, which I did. All was good until the weather/temperature changed and symptoms you describe started to happen.

I discovered that I had very slightly overtightened two screws either side of the spindle bridge in the speedo. I backed them off, problem solved.

[Linda Carr]

On 6/7/2023 at 6:20 PM, standardthread said:

Has someone had the speedo apart?

Our Standard 10 box needed stripping and cleaning due to age, which I did. All was good until the weather/temperature changed and symptoms you describe started to happen.

I discovered that I had very slightly overtightened two screws either side of the spindle bridge in the speedo. I backed them off, problem solved.

No nobody has had it apart.  Was working OK when speedo cable broke, fitted a new cable which appeared to be working OK when the speedo started playing up.  Odo is working and recording correct mileage.  We've bought a digital gps speed dial which works very well.  😁

 

Thanks all for comments 

[glang]

Dont forget its quite a delicate instrument, especially the needle side of the internal drive, which has probably been operating now for 50+ years with zero maintenance😳 Bearings are most likely worn and certainly dry...

[65redspit]

Speedy cables did a first class job on mine and, according to the Satnav, it reads spot on too…

[standardthread]

If you have recently replaced the drive cable I would start looking there first to solve the problem. Have you overtightened something, or is there a kink somewhere

Speedo cable DO NOT require excess oil, just the inner cable oiling, them being removed and the oil wiped off, and again, a light oil.

[Tim Hunt]

I only just spotted this thread Linda and am sorry to hear of your speedo issue. It might be worth checking and servicing the inner flexible drive cable according to the attached leaflet from Smiths Industries. Following these precepts certainly enabled me to sort a problem with the TR4A speedo a while back.

Tim

SMITHS The Care of Instruments.pdf

Edited June 12, 2023 by Tim Hunt

[Guppy916]

I used https://www.speedycables.com

to repair my GT6 speedo, a quick turn around and good price

[Tim Hunt]

Speedograph Richfield in Nottingham overhauled and calibrated my speedo in 1994 and apart from one recent issue of an erratic needle, which I solved by servicing the flexible drive as above, the instrument has performed perfectly for nearly 30 years. According to the wife's satnav it is spot on to +/- 1mph all the way up to the NSL and, according to extended tests against km markers over long stretches of motorway the odometer over-reads by just 1.5%.