Tach Problems

Don

Don

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I just replaced my small 2" Sun Tach with an easier to read and much bigger 5" Autogauge by Autometer Tach with a shift light. Older tach was really small and jumped around. The new tach is much easier to see, but still jumps around at idle and higher rpm's. Tach wire is to the box and not the coil. I have an MSD dizzy and coil, and MSD 7 box. I don't think we wired it wrong, but might be wrong. Any suggestions on what may be causing the jumping around? At idle is bounces from 1k to 3k. The box has a rev limiter built in so I'm not worried about twisting it to high. TIA for any help
 
mine does that in the VW, but thats because the power source for the tach is on the same circuit as the turn signals/horn and other BS.... hit the turn signals, tach goes crazy.

just an idea

Jason
 
I have a Dolphin in the BBC & have the jumping problem when cruisin' easy. (running around 2500 & it jumps to 4000 & sometimes sticks) :gnasher: Mine is wired into the tach term. on a stock Cad HEI.
When I asked the 'tech guy' @ Dolphin, he said it couldn't be grounded with anything else, :bs: so I grounded it to the other side of the car. Didn't really help. :curse2:
I'll be interested to see some of the answers to this one. :yes:
Al :cool:
 
This might be some help, Quote from the MDS website: "If your tachometer doesn't read correctly after installing an MSD, you may need a Tach Adapter. On GM vehicles, first remove the tach filter. There are two MSD Tach Adapters. Contact MSD Tech with the manufacturer of your tach and what you have installed on it to determine which Tach Adapter you will need."

Links to the 2 differrent tach adapters:
#1- http://www.msdignition.com/pdf/8920_frm22049.pdf
#2- http://www.msdignition.com/pdf/8910_21247.pdf
 
This may not help you but make sure all your battery/alternator connections are good and that the wires are all in good shape. Also check the voltage at the tach power wire, make sure it's good.
 
Don,maybe you've already tried it,but run the tach's ground wire all the way to the engine block. G-bodies have lousy grounds to the body/dash and cause trouble sometimes.  :crossfingers:

  Terry
 
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