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TR2/3/3A Fixed the tach on my TR3...Sort of

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martx-5

martx-5

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Before I did the resto, my tach worked flawlessly, so all I did was take it apart enough to clean things up. I never messed with anything inside. After I put everything together, The tach bounced around and made funny noises, so I just disconnected the cable at the distributor, as there were other things to attend to after getting the car together.

Today I decided to see what was going on with the tach. I screwed the cable back in to the distributor, and the same bouncing and noise. I then unscrewed the cable slowly from the tach end as the car was running, and after a couple of turns, the tach started acting normally with no noise.

I read about lousy cables. Is this what I've got here??? Too long???

Who has the proper cable for these tachs?? The one I have is from Moss.
 
I did the same thing on my speedo. A bad cable is better than no cable at least!
 
Well if loosening the cable nut made the tach run better, count how many turns from tight you had to go for things to work correctly.

Most Smiths tachs and speedos that I've seen (with thread on cables) have 1mm pitch on the threads. So, if you unscrewed the cable 1.5 turns, that's 1.5mm or roughly 0.060". You can make a washer that thick and place it inside the speedo cable nut so you can tighten it up and not worry about the distance/gap changing.
 
Generally, it means the inner cable is too long.
First thing I would do would be to probe the cable sockets in the dist and tach head to make absolutely certain something isn't in there.
Mud-dauber or paper wasp.....piece of styrofoam, rock....who know.
If that doesn't fix it, as stated, a washer will do it.
Or, if you're feeling brave, grind the tip off carefully (but that's permanent).
If it worked before, the cable did not magically lengthen during the restoration!

Did you take the tach drive apart on the distributor?
There is a reason for the question.

Dave
 
Alternately, you could stuff an O-ring (*slightly* larger O.D. for a good snug fit) in the I.D. of the cable's dizzy threaded end. Seals and spaces it out at the same time. :wink:
 
Yes, the repro cables are not very good, not even the gray ones. Aside from protruding too far into the drive and the driven instrument, I have noticed that the shape of the formed ends is not exactly correct. Another issue (just happened to me yesterday) is that the outer sheath loosens where it's crimped to the ferule. This results in some interesting sounds.
 
I tried loosening at the distributor end, but that didn't do anything. I like the idea of a washer up at the tach end. Thanks guys.
 
The reason I asked if you'd opened the tach drive, is the bushing....there is a setscrew holding it in. I cannot remember if the bearing dimple for the setscrew is with the bushing pressed agaings the collar on the gear or not.
If you loosen the setscrew, pull the bushing (threaded on the end where the cable threads on) and tighten in a position where the tach doesn't jump, you should be fine.

The other thing I would like to know, is if this only works (no jumping) with the cable loosened at the tach end.
If so, see if the outer housing is jumping around when you drive.
If so, good chance the end is buggered, either bent or offset, and loosening the cable just allows the wobble to be taken up in the housing instead of binding in the tach proper.

Been a lot of years.

I also thoughgt the tach cable was the same on 2, 2A, 3 and 4?
 
TOC, I sent you a PM, Tinkerman
 
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