'78 SC- Alternator or voltage regulator?

[LanceS4803]

I've had fluctuations in headlight output, which concerned me.
Using the Bently manual, I tested my voltage regulator. Tested at 14.35 under no load and 14.18 under load.
Am I correct that this indicates a faulty voltage regulator?
Also, the manual said that to remove the VR, just pull straight up. But this thing does not move, at all. It seems to be attached to the mounting bracket. Is this a different type of VR that is integral to the mounting bracket?

[James Brown]

If it is putting out 14+- volts, it's good. What's the battery voltage, static, engine not running, no load? Could be a ton of things like bad grounds in the headlight circuit. Put a voltmeter on the battery and drive around keeping a eye for any fluctuation. The alt light ever come on above 1k rpm?

[boyt911sc]

Originally Posted by LanceS4803

I've had fluctuations in headlight output, which concerned me.
Using the Bently manual, I tested my voltage regulator. Tested at 14.35 under no load and 14.18 under load.
Am I correct that this indicates a faulty voltage regulator?
Also, the manual said that to remove the VR, just pull straight up. But this thing does not move, at all. It seems to be attached to the mounting bracket. Is this a different type of VR that is integral to the mounting bracket?

Lance,

Your voltage regulator is mounted and held by a single metal screw to the car's body panel. There is a three-wire plug connected to the bottom of the VR and you could pull the electrical plug away to separate it from the the VR. BTW, the VR seems to operate normal based from your readings.

Tony

[wwest]

"...headlight fluctuations.."

Tach bounce, bouncing also...?

After hours, HOURS, of trouble-shooting the battery charging problem on my '78, replacing the regulator and removing the "filter" module mounted just below the regulator, I finally resorted to removing the alternator. What I found inside the alternator was a real surprise. Much of the wiring from the stator to the diode set had the insulation burned off and was apparently randomly shorting out when the car hit bumps in the roadbed. The resulting low output voltage of the alternator would result in the regulator "pumping up" the rotor current but then shortly thereafter the short would open and the alternator voltage would go into orbit briefly.

I bought a replacement alternator w/internal regulator off of Ebay.

But by that time the CD ignition was also toast.

The primary symptom was that the engine would just randomly quit, mostly when traveling on a bumpy roadbed. What was happening was that the over voltage spikes were causing the engine rev limiter to latch up and shut the fuel pump off. Switch off the ignition fully, count to ten slowly, restart the engine and everything would be fine until the next "bump".

The CDI ignition does not have over-voltage protection of any kind so when the alternator output spiked to >16 volts the CDI would start generating random ignition firings, the tach bouncing, firing too close and the rev limiter would latch up.

Be carefull of that tach bounce, bouncing.

In the end, for me, the base problem had been the random shorting inside the alternator.

[47silver]

Remove the alternator and voltage regulator.
Take them to an alternator shop and they will check them. If the alternator has > 20000 miles on it have it rebuilt and you will be a happy person for the next 5 years.