TR2/3/3A Can't get zero on speedometer 60K tr3A

[2liter4cyl]

I'm taking the wraps off my TR3A for spring tune up and lo and behold, the speedometer is at 17mph. I jacked up a rear wheel and went through the gears, shut off engine, and falls back to 17 mph again. How do I get it to fall to zero. Any advice? Thanks. Le T

 

[dklawson]

Since the speedometer is mechanical, a reading other than zero when stopped indicates a problem internal to the gauge. It could be as simple as dirt and grime on the needle bearing for the shaft the needle is on. If you are OK with the idea of servicing your car's gauges, Google for the 27 page PDF on repairing Jaeger & Smiths by Anthony Rhodes. It is a must-have read before opening a mechanical tachometer or speedometer.

If you don't want to work on your speedometer then it is time to send it away for service.

 

[TR3driver]

What he said. In my case, it was the sealing ring between the glass and face, which had shrunk until it interfered with the needle.

Here's one copy of the document by Tony Rhodes.
https://drive.google.com/open?id=0B2H2NJt34OffdDdVSXR0YUFTU3M

 

[glemon]

Before you go too far try loosening the knurled round nut that holds the cable on to the speedo half a turn, sometimes if you have the cable pushed in too far it binds. No guarantees, but worth a try.

 

[2liter4cyl]

Thanks, guys, I had read the Rhodes info before I posted, but hesitated to do anything without some advice. I overhauled the whole thing about 5 yrs ago, when the input shaft froze and the cable broke at the head. This time, I feel the pointer is loose on the shaft. After resetting to zero a few times it has crept up again. I would like to put a small dab of nail polish on the shaft, not to glue, but to make a tighter fit. I presume a small preload on the post is best. Road rallies are in my distant past, so calibration is not too important. Le

 

[dklawson]

If memory serves me, there should be a little piece of music wire that pokes through the gauge face to act as a needle stop (near zero). Just below that on the face of the gauge you should find a small white dot. It is my understanding that you place the gauge on its back (face towards the sky) and place the needle on the shaft oriented so the needle is pointed at the dot. Then you press the music wire stop "down" so you can move the needle to the "other side" of the stop. That should get you back close to the calibration if the gauge was accurate before.

The needle is supposed to be a light press on the shaft. I anticipate that if you put nail polish on the shaft to build up the shaft diameter, it will probably be too thick. Though you were trying not to "glue" the needle in place, you could put a little dab of nail polish on the BACK of the needle once it is installed. (Protect the face of the gauge with a sheet of paper or note card so you don't get the nail polish on the face). The nail lacquer should be brittle enough to break when it is next time to remove the needle.

 

[CJD]

Doug is right, except it's easier to gently lift the needle over the stop rather than moving the stop.