tach problem still!!!!!

[aloha]

305 gm engine, points ignitionI
have been having a problem with my tach pegging the needle when the ignition is turned on. I ran a new wire from the coil to the back of the tach. Sam e problem

Bought a new tach, same problem. Switched the wire on the coil from one side to the other. The tach needle did not move.

Checked and I have from the ignition switch to the tach with power. from the coil to the tach, with power. The only thing that I have not changed is the ground on the back of the tach. The ground is hooked into the rest of the system ground. Everything else works and the engine runs great.

Help me with ideas
Aloha

 

[Chris1956]

Re: tach problem still!!!!!

Aloha, It is either the tach, the voltage or the ground. You have tried everything but fixing the ground. That is what I would try. It doesn't take many ohms to foul up a 12 V system

 

[Barnacle_Bill]

Re: tach problem still!!!!!

Send lead on the tach should go the the neg side of the coil. It works off the action of the points opening and closing. If there is a setting on the back, it should be pointing to 8C (I'm assuming a 305 is 8 cyl).

 

[b00tstrap]

Re: tach problem still!!!!!

If the ground was bad, you probably wouldn't peg the meter, rather you wouldn't get a reading at all or it would be intermitent. If you are pegging the needle, then be sure that your lead to the coil goes to the "-" side of the coil. Also, many tachs aren't compatible with aftermarket high performance coils like MSD or Accel. Lastly, check the settings on the tach for either a 4,6,8 cyl setting or a PPR number (pulses per revolution) and use the manual to set to the appropriate value for your block.