tach needle jumps and flutters

[james r mullins2]

after install a one wire hookup alternator. my tach needle jumps and flutters so much it is had to tell what rpm the engine is ideling at and shift rpm points. i am useing msd 6 al box, wires, coil etc. i just installed two electric cooling fans at the same time as the alternator. i have tried the msd noise filter on the 12v line that feeds power to the msd box. if i disconnect the alternator the tach works fine.

any ideas or suggestions greatly appreciated.

thanks

[500LbGorilla]

Seems to me that the alternator is suspect. Tachs are sensitive. Have you put a meter on your alternator to see what it's doing?

[Mitch]

Check all your connection from your tach, especially your lead to the coil. Maybe you knock it lose when you installed your alt.

[james r mullins2]

Check all your connection from your tach, especially your lead to the coil. Maybe you knock it lose when you installed your alt.

i have checked all wire connections. pick up for tach at the 6al box.
will have my brother ck out the alternator when he gets the time.

[james r mullins2]

yes the alternator is causing the problem. no loose wires , i pick up tach feed from msd 6 al box. i have tried a capacitor on the alternator feed line. solves about 75% of needle flutter. what else can i try, or get to solve problem? this is the second alternator to cause this problem.

[500LbGorilla]

Check all grounds. Take the battery ground to frame loose, clean it, and re-secure it. Make sure the transmission strap ground is good too. Clean it and secure it. Those are possibilities. Try running a ground cable from the frame or a tranmission mount to the engine. Use the case nut right next to the distributor clamp. If you have a bad ground, one of those should help.