Tach series V

[Acollin]

My tach has decided to not work properly. It jumps around but it is clear that is no where near reading correctly. Twitches around a lot at around 1k and can jump to over 5k. If there was a cable, I' d grease it or replace it.

I have spent a lot of time under my dash of late--new dash pad and windshield gasket and was wondering if I could have done something or is it simply time for a rebuild?

Is there anything I should be checking-- did I loosen a ground-- could I have a damaged wire at the coil-- somewhere?

The needle moves-- just in ways that one would not anticipate.

Thanks
Andrew

 

[Tom H]

Andrew I can't think of anything outside the tach that would cause it to jump erratically to 5k. The one major external problem is that sometimes the tips of the steel U-clip that the coil wire loops around on the rear of the tach can get loose a bit or fail to maintain contact with the tips of the inner c-clip protruding from inside the tach. That is a common problem causing the tach to not read.

Most likely the problem is some internal component, probably C2, the main capacitor that sets the pulse width of the tach. For more details about the tach see my article in the articles Archive:

http://www.sunbeamalpine.org/downloads/alpine_tach_repair_rev5.pdf

Tom

 

[T L Alfreno]

Very well done Tom. My tach (Alpine V) works intermittently. Tapping the bezel or hitting bumps turns it off & on. I've tried insuring that the ignition wire coil is making good contact and it seems to be. My next step was to go through the internals and see if I can find a broken solder joint. After reading your article, I'm thinking now would be the time to replace the components. You mentioned in the article that you put together kits with the needed components. Are they still available and how do we go about making the transaction?
Terry

 

[Tom H]

Terry, it could be a loose solder joint inside, and I recommend doing the upgrades I describe. When you note that the "Ignition wire coil" seems to be making good contact, I hope you mean the steel c-clip that the the ignition wire loops thru.

Yes I still have the kits available. $11, incl shipping. Send me an e-mail: tahayden42 AT live.com

Tom