9 replies to this topic

[Chris1275gt]

The pointer on my 1275gt has started moving very slowly the mileage is still accurate. Anyone any idea of a quick fix for this or is it a case of getting it refurbished.

[gazza82]

Might have too much oil being pulled up from cable ..

[Ethel]

Can't see how it could move slower than the vehicle speed without being inaccurate.

 

What's it actually doing? It's driven magnetically against a return spring, so if it's slow returning to zero it would likely be something causing drag. If the odometer is accurate it can only really be in the speedo itself.

[Chris1275gt]

Can't see how it could move slower than the vehicle speed without being inaccurate.
 
What's it actually doing? It's driven magnetically against a return spring, so if it's slow returning to zero it would likely be something causing drag. If the odometer is accurate it can only really be in the speedo itself.

From a standing start it doesn’t move until I’m doing about 10 mph it then slowly increases when the cars speed increases it slowly returns to zero when I stop. The actual odometer is accurate against a sat nav over the 10 mile distance I travelled.

[mad4classics]

I think gazza82 is on the right lines; sluggish operation could be oil getting into the speedo.

 

The original Smiths care of instruments makes interesting reading (Sorry - couldn't find the document on a UK website; just new the name I was looking for)

 

http://vintagebritis...Instruments.pdf

[Ethel]

Simplest would be the needle being loose or something pressing on the mechanism & adding friction.

 

They're delicate things, but if you decide you have nothing to lose in having a go:

 

chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://obswww.unige....eedo_repair.pdf

[slidehammer]

Could the cable be failing? I just replaced one as the needle fluttered below 20 - 25mph then smoothed out, once I changed the cable it was as smooth as anything from walking pace upwards, The other thing it could be is the speedo shaft starting to seize up through either lack of lubrication or old dried up grease. I also had that and freed it up with a very, very small amount of WD40 and a screwdriver in the square drive and gently spun it around.

[Chris1275gt]

Could the cable be failing? I just replaced one as the needle fluttered below 20 - 25mph then smoothed out, once I changed the cable it was as smooth as anything from walking pace upwards, The other thing it could be is the speedo shaft starting to seize up through either lack of lubrication or old dried up grease. I also had that and freed it up with a very, very small amount of WD40 and a screwdriver in the square drive and gently spun it around.

I changed the cable yesterday just in case as the odometer works fine but still the same. I plan to stay off the pop tonight and take it out tomorrow and see if anything is mucky or gummed up or dry or obviously doesn’t look right.

[KTS]

The Smiths Magnetic section on this site is very useful if you're wanting to do any work on the speedo unit


https://www.magnetic...r.com/index.php

[Chris1275gt]

The Smiths Magnetic section on this site is very useful if you're wanting to do any work on the speedo unit


https://www.magnetic...r.com/index.php

Took the speedo out yesterday found a mound of grease at the cable and around the pawl and hair spring which was a pig to get clean. Refitted went for a spin today and all good. Thanks all for advice especially KTS for that link.