Speedo problem

[morimac]

After 500 problem-free miles on the motorway in my '71 van, the speedo needle started bouncing all over the place and, after a few minutes, sank to zero and moved no more. When I got home, I replaced the speedo cable (the old one was broken just at the gearbox end). I also tested the speedo with a drill and, although the needle did move smoothly up as the speed of the drill increased, there was a lot more resistance to the drill than I expected. When I reassembled everything, the needle responded sporadically and there is a loud squeak from the speedo. Bizarrely, the needle will stay at zero then jump and waver to the correct speed when I take my foot of the accelerator. I have run the car with the speedo disconnected and the cable end turns regularly, so I have a feeling the speedo itself is the problem. I have taken it apart and can see nothing obvious and have lightly oiled it but all to no avail. Am I missing something obvious? Should it be so hard to turn the speedo with the drill or should it be almost frictionless? Any advice appreciated.

[bmcecosse]

The difficulty is obviously in the turning of the mileage counter. Have you oiled that? Any I tried spun up very easily with the (reversed) drill.

[morimac]

Thanks. I hadn't thought of that. I'll take it apart again and try oiling/freeing up the mileage counter. After a few loud squeaks this morning, the needle is now completely dead. I fear that the new cable may have snapped with the strain of turning the speedo head. I'll let you know how I get on once I get another cable.

[morimac]

Oiled the mileometer with spray 3 in one (which was about the lightest oil I had kicking around). I then gave the speedo a good blast with the reverse drill and it now turns much more freely. Unfortunately, the cable had indeed snapped with the strain so the second replacement is on the way.

[morimac]

Replacement cable installed and speedo needle now reading smoothly. Many thanks for your advice.

[bmcecosse]