'64 Tachometer Test

[California L33]

Is there any easy way to test a '64 tach? Mine has worked off and on since I bought it 20 years ago. There seems to be no rhyme or reason to its functioning- in other words no pattern. It can work for days on end, and not work for weeks. It can run when cold and stop when hot, or vice versa. It can kick on randomly for two minutes in an hour drive, or work for an hour drive with two minutes off.

I put a cheapo speed shop tach in it many years ago, but it's finally konked out. I'm interested in getting the factory tach working now. I'd always assumed the tach was going bad. Just the other day I started wondering about the wiring. Is there any easy way to tell which has the fault?

[hotshoe]

I dont have any explanation for your problem but I can tell you I have one just like it!! I've checked all the wiring and cleaned all connections and still it does what it wants. Hope someone has a answer for this. :dunno

[dq409]

I dont have any explanation for your problem but I can tell you I have one just like it!! I've checked all the wiring and cleaned all connections and still it does what it wants. Hope someone has a answer for this. :dunno


Old and worn out comes to mind !!

If you really want the stock unit to work,,, send it off and have it up-dated.

Don`t know if anyone reworks the stock guts in module,,,,

If thats what you want find a local old time radio/tube/electronic shop to give it a look over ,,, dq

[California L33]

Anyone have any idea where to find the schematics for one? The shop manual doesn't seem to have the schematics for any guages, wiring diagrams to the guages, yes, but not the internal diagrams.

[jim_ss409]

I don't know anything about those tachs but these guys repair them. http://www.williamsons.com/

[SteveD409]

My theory (I know--who cares :rolleyes: ) is that because all needled instuments like this use a D'Art.... somethingorother (I did a paper on him a long, long time ago----to long as it turns out :D ) mechanism that works on magnetism. The needle sets in little tiny 'bearings' and it's my feeling that these bearings get rusted or corroded enough where they empede the movement of the needle.

And then, again, maybe not.

SteveD

[California L33]

Interesting- that would explain why they wouldn't work. That would explain why typical electronics type trouble shooting doesn't seem to apply (works when warm, not cold, etc.). It would explain why it could suddenly start working on a drive- hit a bump and dislodge the corrosion, but it wouldn't explain why it would suddenly stop working after it started- hit a bump and relodge the corrosion? But maybe just general wear on the bearing surface would account for it all. It's too bad nobody has schematics, because while I'm not the most gifted wrench turner out there, I'm pretty good with electronics- but you gotta' know how it works before you can figure out why it's not working. I haven't torn one apart, but I imagine they could be as simple as a single amplifier for the pulsed DC coming in routed to an electromagnet that causes the needle to deflect, and probably a filter to keep the needle from moving too fast.

[SteveD409]

"...but it wouldn't explain why it would suddenly stop working after it started".

That's like a watch that you wind, then shake and it runs for a little bit, but then stops. Once it was running you would think it would continue to run.

Of course you have to be old enough to remember wind up watches :rolleyes:

SteveD