my 72 deville has pulsating headlights and dash lights... anyone know what might cause this and how to fix it? thanks.. -bill

If I remember correctly this is caused by bad diodes in the alternator/ voltage regulator.

It is 32 years old :)

any idea if i have an external or internal voltage regulator? or how to tell? do new diodes come in an alternator rebuild kit? will this problem eventually lead to me being stranded on the side of the road unable to start my car?

It has been a few years ago, but the problem is in the voltage regulator. This is a piece that plugs into the back of the Alternator and available from most all Auto Parts Stores. The cost in 2002 was about $38.00 to $40.00 dollars. Much cheaper than buying a $375.00 new Alternator.

If you look at your Alternator, you will see the Voltage Regulator attached to the back. It is usually black in color and has some connection posts on it.

Before removing the Voltage Regulator from the back of the Alternator, SHUT OFF YOUR CAR, and DISCONNECT YOUR BATTERY.

You may have to loosen the Alternator to allow it to move into a better working position to get at the Voltage Regulator. In some cases, you may have to remove the Alternator from the car to be able to change the Voltage Regulator.

Make yourself a sketch of the wires and where they connect. When you install the new Voltage Regulator onto the back of the Alternator, look at your sketch to be sure to get the wires reconnected in the proper place.

The Voltage Regulator plugs onto the back of the Alternator. Some have a hole in the center that slides over a threaded bolt. Once the Voltage Regulator is snuggly plugged in a washer and nut goes onto the threaded bolt to hold it securely in place.

Reconnect the wires and retension your Alternator or reinstall and retension your Alternator as the case may be. Then reconnect your battery and start your car.

Turn on your headlights and take a look. The pulsating should be gone and the lights should be bright and steady with no pulsating effect.

While you're cruising around, stop by and have a cup of coffee.

http://members.cisbec.htm/samait/coffee.htm

Happy Motoring!

Sam

The external voltage regulator alternators had the 2 wire plug entering the back of the alternator. The internal regulator ones had the 2 wire plug enter from the outer diameter of the alternator usually at the 11 o'clock postion. Pulsating lights could be the circuit breaker tripping inside the headlight switch because of too much load on the switch, corroded ground, lack of ground? or short in the headlight circuit.