[British-cars] TR4 mechanical tachometer stopped.

[pethier at comcast.net]

On the test drive to prove to myself that I had repaired the ignition, TR44SUE had another surprise for me:  The rev counter stopped counting revs.  No, I don't believe that this is related to my ignition work, as the tachometer is mechanical.  The tachometer drive comes from the base of the distributor, and I did not take apart the distributor to that extent.

Unlike my speedometer, which has been very jumpy since I bought this TR4 in year 2000, the tachometer has up to now been very steady and accurate (checked against mile-markers).

What's the most likely cause of sudden total failure?  Broken cable?

I assume I can disconnect the cable at the distributor end, start the car and determine if the distributor-driven connection is rotating.  Any tricks to this?

Can I put an electric drill motor on the cable to test the cable/tachometer combination?  

Which direction to I run the drill motor?  

Will I ruin something if I accidently go the wrong way (on a speedometer I would not ruin things, it has to deal with the car reversing)?

--
Phil Ethier  West Side  Saint Paul Minnesota  USA
1962 Triumph TR4 CT2846L, 1992 Saturn SL2, 1993 Suburban,
1994 Miata C package
pethier [at] comcast [dot] net    http://forum.mnautox.com/forums/
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I decry the textmessagization of the American-English language.