Team Chevelle banner

No charge problem rectified....

708 Views 1 Reply 2 Participants Last post by  undee70ss
No Charging Condition - Easy enough correction...

Hey Guys...

Been awhile since I posted and though I would add my experience with a no charge problem and pass along the I have gained so much here over the years. Perhaps saves a fellow Chevelle lover time and money.

I recently replaced my water pump on the '68, Used a pressure washer at home to get all the crud and gunk - now that I had room without the water pump in the way. Soon after, I started to notice a no charge condition, via my digital cabin temp/volt gauge I got as a incentive. We have all seen these little gadgets about. (Perhaps I blew into the Alternator some gunk and screwed it up...I don't know.)

It flashes when the voltage is below 12v...and I noticed that it was flashing 11v. Odd. I gun the engine and no change. I see my amp gauge, and it's on the negative side...and does not change when increasing the RPM's.


Electrical problems can be hard to trace and I'm hoping this will be easy.

I check all the battery, at the alternator at the Voltage Regulator. Nothing. I take a multimeter reading at the says now 10v. I gun the engine carburetor side...and just a slight increase to 10.3v. I check behind the alternator a feel for a slight magnetic tug with a screwdriver...nothing.

This is the same alternator that I have had since I got the car 12 years ago. So perhaps it's time for a replacement...and I do, along with a new Voltage Regulator.

I replace the alternator, connect the three wires, belt it up...and the same condition. No charging...and I'm now reading 9v. Now, I'm concerned, as I only now have one more easy viable solution left. I remove the Voltage Regulator...looks a bit rusted in the back. I clean the ground points on the front cowl wall, and the contact points on the plastic tab that snaps into the they are a bit rusty too.

As an additional edge, I connect a separate ground wire from one of the mounting bolts on the Voltage Regulatorto a bolt on the front cowl...just in case the mounting bolts lose their ground. ( Can't have too many grounds I say.)

I start her up...and immediately, I get 13.5 v in the interior cabin temp/Volt gauge. The amp meter also now is in the positive charging side of the meter. I go out and measure voltage at the battery and it shows me 13.8.


It would appear, that the culprit here was a faulty or loosely grounded Voltage Regulator. New VR cost $15.00 and new "rebuilt" alternator was $39.00. No regrets in replacing the alternator, as perhaps the old one was fine, but just a piece-of-mind thing.

13.5 Volt Joe
See less See more
1 - 1 of 2 Posts
You could have field tested the alternator to determine that it was good.

This was written by another member, a very good write up on how it works and how to troubleshoot a externally regulated charging system.
Peter F said:
I dug this out from before, hopefully it help. If not, just post or send me your questions.

I'll try to provide a simplified explanation of how the externally regulated alternator and regulator work here. This explanation starts from a parked car with engine off state.

The regulator brown #4 wire is connected through the light bulb to 12V whenever the key is in the ON position. The other end goes through a set of points in the regulator and then out the F terminal to the field winding in the alternator. So some current begins flowing in the field winding from this connection. The little bit of current flowing produces a weak magnet field in the alternator and also lights the bulb.

When you then start the car, the weak magnetic field from above begins rotating which makes the alternator producing a little bit of voltage. This voltage is fed from the alternator to the regulator on the white regulator #2 wire. This wire connects to a coil in the regulator and turns on a contact when the voltage goes above 3.2V.

Once the contact turns on in the regulator the #3 and #4 terminals are connected together. Terminal #3 is battery power so this puts battery power on both sides of the bulb and turns it off. This means the brown #4 wire should go to +12V. Also, this connects the field terminal right to battery power but still going through the points.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the points I kept mentioning. Then the voltage drops and the points close again. This on-off cycling happens rapidly and is how the voltage gets regulated.

From the above (KOEO = key on engine off and KOER = key on engine running).
F or #1 terminal (field) - KOEO = #4 slight voltage, KOER = 9-12V typically
#2 terminal (sense) - KOEO = 0V, KOER = >3.2V
#3 terminal (Battery) - KOEO = 12V, KOER = 12V
#4 terminal (light) - KOEO = F slight voltage, KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but could be up to 14.5V when engine is running.

Check the light: Ground the brown #4 terminal wire at the regulator. When grounded the light should come on. If you don't have a light then skip this test. Test this with the connector off the regulator.

Checking the alternator: Jumper the blue wire F terminal to the battery post on the back. This should make it easily crank out 16+ volts. Next, connect a troublelight between the battery post and the F terminal. The light should come on and you should measure > 3.2V at the other alternator terminal. If it passes these tests, then it's in the regulator or wiring.

Checking the wiring: At the regulator connector jumper the brown light wire (#4) to the F terminal (#1) and you should be able to measure >3.2 volts on the other alternator terminal or terminal #2 of the regulator connector. If these tests pass, it is in your regulator.

When doing these tests, make sure you turn off or pull the fuses for any added electronics that you can. The alternator test can produce enough voltage to damage stuff.

1 - 1 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.