Speedometer fault.
Posted: Sun Jul 17, 2016 3:56 pm
Hi,
Hopefully someone can shed some light on this problem, or at least suggest a possible cause. The car is a 1973 Plus2S 130/5 speed.
Basically the speedometer started erratic behavior in about 1979! The car was laid up shortly thereafter.
When rebuilding the car I remembered the issue and tested the speedo out with a drill on the end of the cable. It worked perfectly on acceleration, de-acceration and steady speed. I removed the drive mechanism and couldn't see any problem there so just cleaned and lubricated the cable and replaced everything.
However once back on the road the problem was still there. I removed and opened the speedo up. It was very clean and all parts worked freely. I lightly lubricated according to the instructions and didn't expect any improvement - there wasn't!
Studying the movement of the needle more closely, the issue appears to be load related. On acceleration the needle stalls then on lift off jumps to the correct speed. The needle remains steady on over-run or coasting downhill but when any load is applied the needle drops but jumps back as soon as the foot is lifted.
Could it be that some sort of gearbox wear is causing drive to be lost from the mechanism under load conditions?
Any ideas appreciated.
Dougal.
Hopefully someone can shed some light on this problem, or at least suggest a possible cause. The car is a 1973 Plus2S 130/5 speed.
Basically the speedometer started erratic behavior in about 1979! The car was laid up shortly thereafter.
When rebuilding the car I remembered the issue and tested the speedo out with a drill on the end of the cable. It worked perfectly on acceleration, de-acceration and steady speed. I removed the drive mechanism and couldn't see any problem there so just cleaned and lubricated the cable and replaced everything.
However once back on the road the problem was still there. I removed and opened the speedo up. It was very clean and all parts worked freely. I lightly lubricated according to the instructions and didn't expect any improvement - there wasn't!
Studying the movement of the needle more closely, the issue appears to be load related. On acceleration the needle stalls then on lift off jumps to the correct speed. The needle remains steady on over-run or coasting downhill but when any load is applied the needle drops but jumps back as soon as the foot is lifted.
Could it be that some sort of gearbox wear is causing drive to be lost from the mechanism under load conditions?
Any ideas appreciated.
Dougal.