I have a 1967 Mark 2 3.4 litre. The ignition light on the speedometer lights intermittently while I'm driving. The Amp guage needle is either pegged on "C" or on the mark in the middle of the "C" range of the guage. The car is running fine and all electrics are working. I did install a modern radio in the car but no external ampliphiers of any other current draing devices. My question is: Is this serious and if it is where do I start trouble shooting.
Thanks in Advance.

Ray Suchta

Submitted by rsuchta@irwinb… on Wed, 10/03/2007 - 14:44

I removed the cover of the Voltage regulator. Nothing appeared to be sticking or pitted. Indeed, all "guts" were shiny and appeared to be new. I just purchased the car and don't know if the regulator was replaced. Let me do a little research on that. I'll ask the seller. Ray Suchta

Submitted by dgustavson@antex.com on Tue, 09/25/2007 - 11:56

Dave Gustavson, Los Angeles

The diagnosis might be the same, if the voltage regulator has mechanical contacts. (Modern regulators are solid state and usually buried inside the alternator.) When diodes fail in an alternator, the ignition light will come on at low speeds, but this would be repeatable, not intermittent. An intermittent connection in the alternator field winding could cause the problem too.

Submitted by dgustavson@antex.com on Tue, 09/25/2007 - 10:38

Dave Gustavson, Los Angeles

Hi Ray,

The ignition light is telling you the generator output voltage is less than the battery voltage. This could be a problem with either the generator or voltage regulator. If the ammeter is pegged on "C", I suspect the voltage regulator contacts are sticking. In the short term, you could clean the contacts up with fine grit silicon carbide sandpaper (like 400 or 600 grit). But once the plating is worn off the contacts, they will start sticking again fairly soon.