Somewhere along my recent 4,500km trip around Southern Africa, my speedo packed up. It had been reading about 20kph low according to my GPS and then the needle started bouncing around a bit before settling firmly at 0.
On the road, I checked for the obvious things; the cable was fine but nothing registered on the clock.
Today I took it apart to see what I could see; getting that ring off is a real effort!
What I discovered is that the gear driven by the cable (which drives another gear, which turns the speed cup and drives another gear or two, finally turning the digits which turns the digits) was spinning on it’s spindle.
Fortunately I had another parts speedo (shown in pics) and was able to swap the part out and all was well.
I’d like to say this was the result of a rigorous, systematic diagnostic process, but the reality is, it was more luck than anything else!
And apart form fixing my speedo (hopefully since I haven’t tried it out yet) I learned how the thing works. If you’re interested have a look here:
https://www.explainthatstuff.com/how-speedometer-works.html
