Rover SD1 Speedometer (Odometer) Reset Problem

The Rover SD1 Speedometer (Odometer) reset button for zeroing the trip milage is located at the 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 cars are well over 20 years old they will all eventually succombe. The fault is due to a lack of lubrication within the mechanism when the tumblers are released for resetting.

Tech guru, Carl Heinlein explains (1999): 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 and causes them to rotate to zero. Over time, lubricant on the arms dries out and friction prevents the wheels from resetting. He advocates removing 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 the module.

With the unit on its back the 4 plastic arms and cams are visible between the wheels and the rubbing surfaces can be lubricated with 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 cool, 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 plastic stick. After a squirt of suitable lubricant, the numbers were rejuggled and the reset button worked perfectly. No mention 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 gum up the works.

So there you have it! A lubricating problem with a choice of solutions. Nice to have a choice, Eh?