Bouncing Tach
Thread Starter
Track Day
Joined: Oct 2001
Posts: 20
Likes: 0
From: Virginia
Bouncing Tach
In my 80SC, the tach "bounces" when I shift gears. When I originally did the PPI, the guy who did it for me said it was no big deal and shouldn't worry about it. I'm just wondering whether it's fixable, still shouldn't worry about it, or should I replace it. Thanks
AutoX
Joined: Jan 2002
Posts: 11
Likes: 0
From: Savannah, GA
This can possibly be attributed to the alternator. I know for sure that an indication the alternator is bad is if the tach bounces when the brake is applied. This is caused by all the power being used (car running, a/c on, radio on, lights on, etc...) If you are reving the engine, i.e. applying power, and the alternator is weak the power flux can cause tach needle bounce. Just a possible source of the problem. Could be other things.
Instructor
Joined: Jun 2001
Posts: 170
Likes: 3
From: Arlington, VA
My 85 does the same thing when I come off of the gas. I asked the shop about it and they said it is most likely the throttle position sensor. I was told not to worry about it until it begins to impede performance or get really annoying. So far not too many people think I'm reving my engine at them while waiting for the light to turn green 
Nate.
Nate.
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Rennlist Member
Rennlist Member
Joined: Jan 2002
Posts: 19
Likes: 0
From: Moorpark, CA
Question - do you have after market ignition system parts? Do you have a good ground of tach components? If possible, get a good volt meter and get a good ground on the tach can. put the neg lead on the tach. Find a real good ground to the body. If any voltage shows up on the meter during the operation (there shouldnt be a bounce) - then the tach is not grounding properly and the meter is telling you how much it is failing. Just a thought. DOUG
