Alternator gauge very erratic.

[Keyeserin]

69 Dart 340. When I start engine alternator gauge jumps all over when idling. If door is open
dome light flickers bright and dim. Any help is appreciated.

 

[Ben Drinkin]

I'd suspect the voltage regulator.

 

[RedFish]

Just wild guesses. Stuff I would be looking at. Voltage regulator itself or it loose at its mounting screws, a loose wire connection ( positive or ground, including the ground strap to firewall ) combined with engine vibration. Even a alternator belt issue.

 

[Darthomas]

That's a bad connection on the bulkhead.
The biggest wire.
Well, if you HAVE a poor connection in the circuit for the heaviest gauge wire in the plug, it will behave exactly as you describe.

 

[str12-340]

I agree - voltage regulator most likely

 

[RPMagoo]

-- 69 Dart 340. When I start engine alternator gauge jumps all over when idling. If door is open
dome light flickers bright and dim. Any help is appreciated. --

-- Good luck. It can become very frustrating. -- See my posts.

 

[jos51700]

Step one: Bypass the gauge and the bulkhead. See search engine on this very site for instructions. failure to do so invites melted wiring and vehicle fires.

Step two: replace (as mentioned) the main voltage regulator. If yours is still electromechanical, it will behave as described. Conversion to solid state is cheap, easy, and well worth it. Again, "search".

Step three: replace instrument module voltage regulator (OE was electromechanical, solid state is a DIY thing, or purchase from vendors found on this site.

For my car, it took all three to get stable lighting and the IM regulator was the major culprit.

 

[BillGrissom]

If you haven't addressed the bulkhead connector issues (search MAD Bypass), it is amazing your bulkhead hasn't already melted in corrosive WI, so jump on that (1963 & 65 owners don't have that issue). The VR needs a good connection to BAT- to work correctly. A rusty factory sheet-metal screw into the body may not get that done after 49 years.

 

[RPMagoo]

-- 69 Dart 340. When I start engine alternator gauge jumps all over when idling. If door is open
dome light flickers bright and dim. Any help is appreciated. --

-- See My post re Flickering headlights - Go to post #12, in that series. -