I just bought my 68 Plymouth Valiant with the plans to restore it. Well I can't even get it home because the charging system is not working. Now this is what has been done to the car before I bought it, new water pump ,new Alternator( yes verified it was a good one), new voltage regulator, and new starter. Now I myself replaced the Voltage Regulator because it wasn't done when the Alternator was replaced. The Battery has been replaced as well.

So my problem is the car still will not charge, I have checked the wires and they are good I tried following the diagram but still have not figured out why the battery would not be charging. Does the charging curcuit go through more than just the Voltage regulator ( i think I saw the diagram go to the starter selenoid) the car starts fine so I think the selenoid is still good.

I am looking for advice and trouble shooting tips on how to locate the problem with the charging system, the previous owner said that the car just stopped charging and he assumed it was the alternator and battery so he replaced those both.

Well I am at a lose and about ready to say the heck with it and I really don't want to give up, but what good is a car if I can't keep the battery charged. And I will be damned if I take it to a repair shop that works on older vehicles, I don't have a few thousand dollars that they may charge here in CA.

 

Here's how this works, assuming it's a stock type 68 system

You have the dark blue "run" or IGN1 wire coming from the ign switch, is "hot" in the run position. On your car, it supplies the ignition resistor, which drops the voltage to the coil in "run." THIS SAME wire also supplies the IGN terminal of the regulator. The only other wire on the regulator is normally green, and goes to the field (push on) connector at the alternator.

A simple test is to take a meter/ test lamp and check battery, then the big stud on the alternator, should have the same voltage.

Then turn the key to "run" and check the ign terminal of the regulator, second, check the other terminal, the "field." You should get a nice bright light, or volage very close to "same as battery" at the IGN, you may get somewhat less at the field.

If this is OK, still with the key in "run" probe the push on terminal at the alternator. Here again, you should get "some" voltage.

If this is OK, take a clip lead and disconnect the field "push on" terminal, hook the clip lead to the exposed alternator terminal, then hook to the big output stud. You should see a small spark, if not recheck a couple of times disconnect/ reconnect.

IF you get a spark, it shows that the brushes are making contact and are drawing current.

If this is the case, leave the clip lead hooked up and start the engine. Gently bring up RPM, watching the ammeter, and if possible, hook your voltmeter to the battery and monitor battery voltage.

This is called "full field" and should result in substantial charge, depending on RPM

If not, you have alternator or wiring problems in the output circuit.

If not charging, put your voltmeter directly onto the output stud. Gently bring up RPM. IF you don't see a voltage increase, you have an alternator problem

If you DO see a big voltage increase, but not at the battery, you have a wiring harness problem

If the "full field" check results in substantial charge/ voltage at the battey, it's time to backtrack to the regulator circuit. Remember, just because a regulator is new, does not equal "good."

Disconnect the regulator. Clip lead the two wires you unhooked TOGETHER. Start the car and check as before. If the alternator and harness are good, this AGAIN will result in a "full field" condition and should show substantial charge/ voltage.

IF IT DOES, you still have a bad regulator.

Also bear in mind that a regulator MUST be grounded to the battery negative to regulate correctly.

 

How would I know if the regulator is grounded? there are only two wires for the regulator the fld and the ign, now there are screws, one on each side of the new regulator, do I need to add a new wire and ground it to the where the battery negative is connected?

 

here are acouple more ideas to check first check your terminals making sure they are not corroded or loose make sure your belt isnt slipping and check for shorts in your lighting curcuits this will cause a slow drain on your battery

 

Make sure they put the correct alternator on it.. Later alternators may look simillar but they are not the same. Would require re wiring to a solid state regulator
Which is what I would do for a reliable charging circuit

 

Well, read my post, I told you in there "how to tell."

But yeah, the general idea is if there is a POSSIBILITY that it's not grounded, and you don't want to actually CHECK with a voltmeter as I outlined, then run at least a no 10 wire from the regulator mounting bolt to the battery negative.

BUT AS I OUTLINED above, IT MAY ALSO BE voltage drop in the positive side of the harness as well.

GUESSING is no way to go through life, my son.

 

THIS IS NOT TRUE

The only electrical difference in the late (1970 and later) alternators is that they have two field connections. ALL you need to do in order to use a 70/later alternator on a 69/ earlier is to make up an easy, short, grounding wire and ground one of the push-on brush connections.

Easy.

 

Thanks for the replies, at 440 I will do all you suggest trust me I want to do it right I just have to wait till after the first of next month till I can get the car towed to the from of my house lol.

 

I hav e the same problem on my 67 valiant. i ran a wire directly from the bat to the alt and now when i rev the engine up to around 3,000 rpms the voltage goes up to about 13.5 volts. where else do i need to be looking at?

 

There is absolutely nothing wrong with charging voltage of 13.5V!!!!

But you really should start a new thread