Bouncing Ammeter

UPDATED 6-18-2014

Some Mark III's experience a problem where the Ammeter needle bounces between discharge and charge very rapidly while at cruising speeds.

It has been discovered that the regulator, as wired from the factory, does not receive the proper voltage to the "A" terminal  (white/blue wire).  The "A" terminal is intended to monitor the current condition of the battery and should receive exactly the same voltage that can be measured at the battery.

To test your own car, turn off all accessories and turn on the key.  Now check the voltage across the battery and at the regulator "A" terminal.  They should be the same within about .2 volts.

If your car has not been modified, you will likely find a 1-2 volt drop at the regulator.  The fix is to find a 12 volt source that offers the same voltage that is found at the battery.  The best source is the large red charging wire.  You can either pick up this source on the back of the alternator, or splice into this large red wire that is in the wiring loom directly adjacent to the regulator.  Be sure to test the new source for proper voltage reading before making the change.  The original white/blue on the regulator can be cut or disconnected and tapped off.


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