Sticking speedometer fixed
Posted: Sun May 18, 2008 11:00 am
I've finally fixed my speedometer. The indicator needle started sticking on a trip up to Edinburgh a few weeks ago and an attempt to clean and oil it without completely dismantling the mechanism was unsuccessful. Matt sent me another one and I rebuilt it yesterday afternoon, but after fitting it to the car the needle immediately jammed (it had worked on the bench). Armed with the knowledge gained from rebuilding Matt's, I rebuilt the one I took off Fenchurch last night and fitted it this morning. It seems to be working OK. It is reading high (75 on the speedo = 65 on the GPS) but I suspect it has always done that.
I think the sticking was caused by a buildup of gunge in the bearing at the bottom of the needle shaft. This is a hole that is tapered at the bottom, into which fits the pointed end of the shaft the indicator needle attaches to. The only way to clean this out properly is to dismantle the mechanism, drip/squirt a grease-dissolving solvent into the hole, jam a bit of paper towel and a pin or a very small brush in there, and repeat until you have washed all the black stuff out (this took quite a while to do on both speedos). Upon reassembling the mechanism I put a tiny amount of very thin 'clock oil' on the end of the shaft.
I'm pretty sure I now know how to fix the one Matt sent me too - there's a tiny screw that adjusts the needle shaft end float, but you have to take the mechanism out of the case and remove the needle and face to get to it. For anyone else thinking of rebuilding one, the trick to setting that screw is to do it while firmly pushing the speedo drive in, otherwise when you fit the drive cable the rotor will be pushed in slightly and cause the needle shaft to jam. Too much end float is less likely to cause a problem than too little here.
I wanted the new odometer to match the mileage on the one I was taking out, so I had to figure out how to 'clock' it without breaking it. After doing it the hard way (completely dismantling and reassembling it - very fiddly), I figured out the easy way: starting from the leftmost number, pull the roller and the one to the right of it away from each other (there are springs holding them together), turn it, then let them go back together, wiggling them slightly until the little drive cog between them reengages. When you're turning the rollers, don't pass 0-9 or you will accidentally change the roller to the left.
A warning: isopropyl alcohol (which I was using to clean the grease and dirt off) dissolves the paint in the numbers on the odometer rollers.
I think the sticking was caused by a buildup of gunge in the bearing at the bottom of the needle shaft. This is a hole that is tapered at the bottom, into which fits the pointed end of the shaft the indicator needle attaches to. The only way to clean this out properly is to dismantle the mechanism, drip/squirt a grease-dissolving solvent into the hole, jam a bit of paper towel and a pin or a very small brush in there, and repeat until you have washed all the black stuff out (this took quite a while to do on both speedos). Upon reassembling the mechanism I put a tiny amount of very thin 'clock oil' on the end of the shaft.
I'm pretty sure I now know how to fix the one Matt sent me too - there's a tiny screw that adjusts the needle shaft end float, but you have to take the mechanism out of the case and remove the needle and face to get to it. For anyone else thinking of rebuilding one, the trick to setting that screw is to do it while firmly pushing the speedo drive in, otherwise when you fit the drive cable the rotor will be pushed in slightly and cause the needle shaft to jam. Too much end float is less likely to cause a problem than too little here.
I wanted the new odometer to match the mileage on the one I was taking out, so I had to figure out how to 'clock' it without breaking it. After doing it the hard way (completely dismantling and reassembling it - very fiddly), I figured out the easy way: starting from the leftmost number, pull the roller and the one to the right of it away from each other (there are springs holding them together), turn it, then let them go back together, wiggling them slightly until the little drive cog between them reengages. When you're turning the rollers, don't pass 0-9 or you will accidentally change the roller to the left.
A warning: isopropyl alcohol (which I was using to clean the grease and dirt off) dissolves the paint in the numbers on the odometer rollers.
