Ok everyone, among other issues, my '73 charger is not charging the battery. It has a 400 and I have already replaced the alternator (65amp) the voltage regulator and the porcelain resistor. The dang this will still not charge the battery when running. The D|C meter is always to the left of center when idling with no lights on, but pegs toward D when the headlights are on and slowly drains the battery to nothing and it stalls out. Does anyone have any idea what I should try next?

I have a buddy that restores chevelles that said unless I use the same alternator that came stock, the power system will not accept it and it will not work. Any truth to that? I believe that a 50amp came on it stock but the guy i bought it from had a 2V alternator on it when my pulley is a 1V.

Please help!! It will drive fine during the day, but whenever I use the head lights it dies after a few minutes, any ideas would be appreciated!!

 

The thing you need to do is STOP throwing parts which cost money, and start doing some troubleshooting. Here's a basic diagram of the 70 and later "isolated field" system:

http://67-72chevytrucks.com/vboard/a...1&d=1206518491

On your car, the wire coming in from the top on this diagram marked ignition. comes from the ignition switch, and is hot in run. Notice that it goes two places, the "top of the triangle" in the regulator connector, and one of the field connections on the alternator. These should be blue

The other field wire should be green and goes to the regulator.

Very important that the regulator case "sees" a good ground

Very important that the alternator you bought is for 70 model year and later.

To troubleshoot, get a meter or lamp, first clamp the meter/ lamp to ground (battery negative) and probe the big stud on the alternator. Make sure it's hot, has 12V same as battery.

Next, turn on key to "run", unhook GREEN field wire from alternator, and probe the EXPOSED TERMINAL on the alternator. It should be 12V same as battery

This shows that the blue wire is supplying power to the field, the power is going through the field, and "coming out" the other side.

If all this is OK, next take a clip lead and GROUND this terminal you exposed (on the alternator) where the green wire was.

Start the car. The alternator should CHARGE FULL OUTPUT, greater at higher engine RPM's and should "put out" pretty much full at "low" or "medium" cruise---about 2000 RPM or less

If this does not happen, you need to get deeper. Either the alternator is bad, or the blue IGN wire is flakey, or the main charge wire (on the stud) is making a poor connection.

If you DO get this output in the above test, shut off the engine, re--connect the green field wire, and now move up to the regulator connector.

Turn on the key. BOTH the green and blue terminals in the regulator connector should show power (same as battery) with the key in "run." If so, sounds like bad regulator.

If not, it's a simple wiring harness problem. Most likely suspect is right at the regulator connector.


If you run these tests, and the thing will not charge, post back.

Your "Chivvy buddy" is nuts. I've run the SAME 70 and later regulator on ANY 70 and later alternator, including the large frame 105A alternators.

I've run Ford regulators on Chivvies, and vice versa. RIGHT NOW I have a 69/ earlier Mopar regulator running a Toyota alternator on an engine conversion-----Toy 20R and 4 speed in an old Cletrac/ Oliver crawler.

This is the huge 105A unit used on Taxis, police, etc, in the middle '70's. It is twice as big and heavy as a stocker Mopar. Used to run it on my old Landcruiser--360/ then 340, finally-318 with this very same type regulator

http://thevbattery.com/cart/images/1...alternator.jpg

 

thanks for the info! I will let you know what I find!

 

Ok, so I checked out some things and here's the gist of it...

1 reads 12v as battery does
2 spade reads nothing when ignition is on or off

4 & 5 both read about 10-11v

I also tried the grounding the green spade (#2) and the voltage meter on the dash didn't budge.

Based on that, would you say that the blue wire needs to be replaced? or might that be a combination of that and the voltage regulator?


(adding that once jump started, it starts and runs fine, just can't use the headlights or it drains it)
Thanks!!

 

You did not mention what 3 (blue field) reads? Should be 12V, key on

If not, wire/ connection problem in the harness concerning the blue wire to no3

If 3 reads battery, unplug 2 (green) and read voltage, key in run, at the alternator terminal. It SHOULD be 12v (good) but I'll bet nothing, because you say you grounded 2 and the "meter didn't budge"

So far, sounds like bad alternator/ bad brushes.

 

I am 99% sure it isnt the alternator because it is literally new out-of-the-box as of yeasterday, unless it was bad right from the start

 

but blue(#3) is reading low single digits it not below 1v. would you be thinking short or voltage regulator?

 

No3 reads 1 volt? At the alternator? and the key is in "run?" That's your trouble.

ALL THE BLUE leads should be the same. They come from the key are "hot in run" and supply 12V to ignition, the blue at the regulator, and the alternator field. If you have an electric choke, it goes there too. In fact if you have an electric choke the harness is probably spliced right there.


Also, alternators CAN BE bad right out of the box!!!!

Easy to check, now that you have your feet wet!!

Just jumper a lead from the big alternator output stud to ONE of the field terminals. GROUND the second field terminal and you should get "full tilt" output as I described earlier.

 

Soooooo The first quick check would be the test on the alternator and then you think I should measure and replace the blue wire? (no trying to be dense, but I want to make sure that I get it 100% right the first time)

 

I should've been more clear. I'd recheck the power on the blue wire, key in run, should be close to battery V. If it is, then try grounding the other terminal.

As a second "double check" you can rig a clip lead from the battery stud on the alternator to EITHER field terminal on the alternator, then ground the one that's left.

The only difference, here, is that when jumpering to the output stud you are eliminating the blue wire completely.

It SOUNDS to me like you have bad brushes/ bad field in your "new" alternator.

Don't EVER assume that a new or rebuilt item is good. New/ rebuilt parts can be defective, although years ago, the odds on a defective were pretty high.

 

Jonny, 440 `s right. I had a 73 cuda w/440. it would go through no start , or run then die phases. I did what you did, its called the shotgun method, throw alot of new parts on and hope you hit the mark. still had problems. i ran jump wires, still same effect. keep in mind all the electrical was new. before the prob. started, then all was replaced again, it was a recent resto. at that time. mid 80`s. so oune time it happens, im under the hood playin w/ wires and I happen to notice sparks shoot out of the NEW starter relay box. grabbed the bat. lead wire to the relay and the terminal ws loose. It was loose, then when Id start it, it would ground against the housing and stick to it so it would run. then would come loose, there were arc traces all around were the terminal came out of the housing. So never rule out new parts not being culprit.

 

got it! Thanks guys! I will let you know what I find!

 

ok, tired the
It pegged out at "C" so I am leaning toward a bad wire then. I am gonna run to the local parts store and undo the wiring harness to figure out where it is all going and hopefully find something horribly corroded for an easy fix.

Thanks again! I'll let you know what happens (once it gets above freezing that is ;-)

 

I think you're getting close Trace out both the blue and green make sure they're OK and I'll bet you're on the home stretch

 

ok, so I pulled the alt to get it checked JUST to be sure it was working right..
it was...
traced the blue wire, IT WAS CUT!!!
spliced it, still didn't work..
as a final JUST to be sure, replaced the voltage regulator AGAIN

BINGO!! It worked!

So after all that, a CUT wire and a broken "new" voltage regulator and it was good to go. Thanks for the info guys!!! On to the next project!!
(see next thread ;-) )