Re: Tachometer reads full rpm w/switch on
Should be three connections on your tach.
One is from the input to the rectifier, thsi will be an a/c alternating current signal.
Another is from your power source, usually from ignition switch in most wiring configurations.
The last is a ground. If any one of these connections are bad or intermittant it will cause your tach not to work correctly, if at all.
You mention the tach stays pegged, is this with the switch just in the on position or after you actually start your engine?
As Ezeke said it is most likely a rectifier problem, have you noticed any wierd readings on your volt meter if you have one?
Check the rectifier circuit with the resistance checks for diodes, sounds Like a good possibility of having a diode short on one leg of the bridge rectifier and you have alternating current riding on your dc circuit, does wierd things to gauges and really plays heck with the batteries also.
Theory wise you will most likely find that one leg of the bridge is shorted on the negative side, thus allowing alternating current to be put to ground potential, drawing excessive current from your stator during the negative half of the sine wave, not good for the stator either.
