“Sluggish” speedo

[Nick Whitehead]

After a lengthy (25 year) lay up, the speedo in my 2l Vitesse is not working properly. As I approach 50-60 it eventually wakes up and creeps towards the correct speed (compared to GPS on my phone). But at lower speeds sticks on zero or creeps towards 20-30.

Any ideas? Is the disk rusty? Are the magnets weakened? I think the cable to the gearbox is ok and engaged properly because the odometer is reading accurately.

Is it easy to service myself if I take it apart, or is it best to try and get a new/exchange meter.

 

Thanks for your advice.

[trigolf]

Hmm..

It's most likely that the grease/lubricant in the innards has dried up with age. Most people send speedo's to specialists for repair/overhaul,as they are mechanically delicate. 

[Colin Lindsay]

Try a spray into the innards with switch lubricant such as Servisol, it won't harm anything but may help it work again.

[Pete Lewis]

hardest is getting the rim and glass to release the old rubber rings grip well and often sticky

you can lube the main shaft the oddo roll worm etc  never take take the needle off the hair spring will unwind and you 

have no idea what tension is needed 

dont grease or get anything sticky on the magnet and drive disc  just a a blast of brake cleaner 

if oiling the needle pivot bearings a drop of oil on a cocktail stick to use as small dropper helps 

pete

failing that its send to Speedy Cables or JDO

pete

 

[ed.h]

On 22/10/2023 at 10:57, Nick Whitehead said:

Is it easy to service myself if I take it apart, or is it best to try and get a new/exchange meter.

 

If we're talking the ubiquitous Smiths magnetic instrument, wouldn't call it exactly easy, but a fairly handy person can likely take it apart, clean it, and get it back together successfully.  Here are a couple of links that cover instruments that should be very close to yours.

http://bullfire.net/GT6/GT6-27/GT6-27.html

http://bullfire.net/TR6/TR6-40/TR6-40.html

Ed

Edited October 24, 2023 by ed.h

[Morgana]

I second that it's likely just gunge from solidified lubricant. I have avoided any liquid lubricant for the actual cable, preferring to extract the inner cable (great if you can do it without removing the outer cable so you don't even have to get under the car) and getting it very clean, before assembling with a little powdered graphite. Assuming the outer cable sheathing isn't rusty and causing the inner to bind, which can be tested with spinning the inner cable with one's fingers.

Any stuck elements in the instrument itself can be sorted as in ed.h's links. I've attached a similar article I've found useful in the past.

I would not advise squirting anything in 'just in case', as it's always worthwhile popping the bezel and checking what the problem really is, while going in blind can end up making things worse.

Speedometer Repair.pdf