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TR2/3/3A Noisy tachometer

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T

Topley

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So when I purchased my car the tach did not work. When I looked into is I found that the cable was disconnected. I connected and it made quite a racket for about a block. then died. The cable broke (I find now) an inch or so from the distributor. Bad cable me thinks and previous owner just disconnected due to noise. Ordered a new cable with housing from Moss. Greased it with bearing grease (up to about 5 in from Tach end) and installed today. Made a racket at the tach within the first 100 yards... so as I was driving I reached under and unscrewed from tach ASAP as I don't want to break another cable. So, duh, I guess... old cable when I didn't know it wasn't connected made no noise so I guess its not surprising that it wasn't actually the cable that was the problem. Tach seems to work (well accurately report RPM's when hooked up.) Any ideas? If I have to remove the tach the left side thumb wheel seems accessible the right not so much, for my fat fingers at least. Any trick for removal and restoration if that's what I need?

Thanks!
 
More than likely it’s dried 50 year old grease causing the problem. The tach will have to come out and apart to clean and re-grease it. The thumb screws are a challenge, but not terribly hard to remove.
 
DIY type of thing once I get the thumb screws off? Couldn’t find much online other than people with broken gauges and places to send them in for repairs.
 
You will find a tr3 tack a simple instrument in many ways, but be advised of the coil spring behind the needle and the shiny dish; yes the problem is probably drying grease. Sometimes getting the glass off can be a challenge, but look at the on line rebuild stuff and PDFs. The noise could be the cable if you are lucky, and I would try that first. In fact you can undo the speedo cable under the dash and move that to the tach to isolate the problem and see if it is the gauge or cable. The instrument are very similar and do not care. Or spend the 20 bucks and get a new cable from one of the big 3 and pop that in because sometimes getting under the dash and unhooking both the cables is a pain. If it is the cable, either get a new one or pull the inner cable out from the sheath and wipe it with a non-fluffy towel and lightly grease it and try it.
 
When we were restoring The Gray Lady, Brian and I had a a problem with short-lived speedometer cables. We eventually learned that the cables we had received were wound in the wrong direction. What I mean is, the inner cable is actually a very long coil spring and this spring has a design direction in which it is wound. So, let's say the correct direction for the cable to turn is CW looking into the back of the speedo. You would want the "inner-cable'' to also have its coils wound in the same direction, CW. If it was opposite (CCW), the cable would have a tendency to bind, which made noise and sort of bunch up inside the outer sheath, leading to early failure. We found that the replacement cables we were receiving had the wrong spring winding direction. We eventually had one of the big 3 suppliers check their stock. Some cables were CW and others CCW. Really! I don't remember which one we needed CW or CCW, but when we got the correct one our problems disappeared. I would imagine the same issue could apply to a tach cable.

I know this sounds crazy, but it is true!
 
So I removed the tach and found that the inner mechanism was loose in the housing. Seems the "goo" they used to seal it way back when had dried up and broken to bits. Those bits we flying around inside (and I assume some were stuck.) I removed all the dried pieces from the inside and the few bits still around the screw holes on the back of the housing. I'm sure its better to have some kind of buffer but when I just reassembled and returned to the car the tach now works smoothly, pretty accurately and quiet!
 
I think that there was a rubber washer between the case and inner mechanism to act as a damper. Most old ones have probable become brittle and brake up as the case is removed.

I cut some discs of very thin rubber to replace the broken washer.

David
 
Glad you got it. I have seen that before were the rubber grommets turn to goo. The first time I saw it-- it took me a while to figure out what was happening that when they melt or dissolve or whatever they do the instrument becomes lose. I kinda remember someone telling me to use Brake Clean on the dish if the goo got on it. I think I held it upside down and sprayed it on rather than take the instrument apart, but again that stuff could mark up the face, but is sounds like you got it.
 
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