Rover SD1 Speedometer (Odometer) Reset Problem
The Rover SD1 Speedometer (Odometer) reset button for zeroing the trip milage is located at the top-left side of the instrument. Since quite early in the lifetime of our cars there has been increased likelyhood of malfunction. Any car over 10 years old may have suffered the problem and now the Series 2 cars are well over 20 years old they will all eventually succomb.
Erstwhile Tech Guru, Carl Heinlein explains (From a 1999 "ROVER" magazine): The fault is due to a lack of lubrication within the mechanism when the tumblers are released for resetting. Pushing the reset button withdraws the gears that drive the wheels leaving them free to spin. Plastic arms bear on a cam at the side of each wheel causing them to rotate to zero.
Over time, lubricant on the arms dries out and friction between the arm and the cam prevents the wheels from resetting
He further describes how to remove the instrument after taking off the binnacle cover, releasing the hold-down screws, removing rearward obstructions, undoing electrical connections, removing the front cover and pushing the speedometer out of the hole in the back of its module.
With the unit on its back the four plastic arms and cams are visible between the wheels and the rubbing surfaces can be lubricated using a very small screwdriver or piece of thin wire dipped in silicon oil (Dot 5 silicon brake fluid). He warns not to get lube in the wrong(?) places or the wheels will not spin freely when the driving gears are dis-engaged. Check the unit zeroes OK, and refit.
That all sounds pretty do-able, but member Joyce Clements (1997) wrote that, after removing the binnacle cover and front perspex cover (not easy, but possible), access can be gained to the front of the speedometer. The tumblers can be moved by hand with the aid of a small pointy stick. After a squirt of suitable lubricant, the numbers were rejuggled and the reset button worked perfectly.
There is no mention by Joyce of what is a "suitable lubricant" so one might speculate that if it were WD40, it would work fine initially but later gum up the whole kit n' kaboodle due to dirt and dust.
However if one used dry PTFE spray lubricant there would be no oily residue to attract any local dust to gum up the works.
So there you have it! A lubrication problem with a choice of solutions. Nice to have a choice, Eh?
Having successfully used Carls method years ago, I find again the tumblers dont readily resetand because I cant face dismantling the instrument housing, I've now taken to bumping the reset button with a rapid finger flick, then, all of a sudden, a row of zeros. Keep flicking, methinks!
If anyone has validated any of these processes or can add an alternative, please contact me for inclusion on this page.