1964 Plymouth Valiant Power Issue

Hi everyone,
I'm working on a 1964 Plymouth Valiant v100 and have some type of power issue with it. The car starts and runs nice at idle, but the alternator gauge either stays directly in the center (if no headlights or other power drawing things are on), or goes down into the "not charging" side if the headlights are turned on. The gauge never goes past the center and up into the "charging" side. It currently has a brand new battery, voltage regulator, coil, alternator, and Pertronix kit in the distributor. I've tested for power at the battery, voltage regulator, coil, and alternator and have power in all of those places.The car will run and drive but when accelerating it runs like it's missing and has a lack of power, and if it stalls while on a drive it barely has enough juice to start again. On a similar note, if I leave the car sit in the garage for a couple days it drains the battery. Does anyone have any ideas on what to try? Thanks in advance!

start with use of a VOM and follow along with sop manual trouble shooting if you are not familiar with automotive charging systems and testing

Your OEM alternator was the round back 36 amp closed field type. So it had only one spade terminal for the one little green wire. Did a part store hand you a later model alternator with two field terminals?

Yes, RedFish makes a great point. The factory style is the round back (early) style. See if you can get a picture of yours from the back so we can tell which one it is.

so, just ground one field lead if using the original style mechanical or replacement electronic regulator for the earlier cars...you can retro the two wire field setup to work on the one wire...you cannot however go the other way...

bigaadams said:

so, just ground one field lead if using the original style mechanical or replacement electronic regulator for the earlier cars...you can retro the two wire field setup to work on the one wire...you cannot however go the other way...

Click to expand...

We're gettin there. Wanted to find out what he HAS first before throwin what might be too much info at him. He may not be familiar with that mod.

go back again to my first reply before even mentioning the forum mentions the two types of alternators, use a good VOM and proper test procedures...if unfounded in trouble shooting...he needs a few diagrams and procedures from the book...he may do best to farm this out if he has no experience in troubleshooting or if he does not have the meter and repair manual, save headaches, components and wiring harness from damage.

but yes, I agree, if the man is not founded in the theory....a two wire could be confusing

I think he need a couple of batteries in the back, and a supercharger in the front, and a 5-point harness.
But if it's a wagon, I'm kindof looking for a new home for my 367

Thanks for replies everyone. Sorry for the delay, I forget to check this when getting back into town from a work trip. I only have one field connector on the back of the alternator. I also called the manufacturer to make sure it's an internally grounded one and it is.

OK here is what...............the single field connector is used up through 69 UNLESS the car has been modified. To see if the alternator is capable of charging, clip your voltmeter to the big stud on the back of the alternator. Start and run the engine and slowly bring up RPM. The voltmeter should rise above 12 on up to about 14 or a little more.

If it is way way high, this indicates the charge output wire is not continous to the battery....such as a bad connection in the bulkhead connector or ammeter

If it stays low, down around 12 or less, it is not charging

If not..........now disconnect the green wire either at the VR or alternator. If you disconnect at the VR, the following test will verify that wire integrity. Connect the wire end to a jumper wire to the battery. You should see a small spark in subdued lighting when you connect/ disconnect the wire. With your jumper connected, again run the engine and bring up RPM. Again monitor voltage, either at the alternator stud or at the battery. Voltage should rise above 12V don't allow it past 15-16

If this happens, the alternator is OK. If the voltage stays low, either investigate new brushes/ bearings or be prepared to dig into the alternator, or replace it

Next, verify you have 12V getting TO the VR. Turn the key to run, engine off. Measure voltage at the VR "ign" terminal. Should be "same as battery"

If this happens, and the alternator was charging in the first test, replace the VR

REPLACEMENT ALTERNATORS

"We" (several of us here) could write a book

UNLESS you are intent on vehicle originality, it is better to get a 74/ later 'squareback' alternator. Also resist getting a huge output, above 45 A or so, because your factory wiring 'won't like it.' You will have to upgrade wiring if you go with a larger output unit

More to come

Some reading:

67dart273, roundback - Google Search:

Round back alternator

Can I use electronic regulator

The short answer is that you can replace your old alternator with EITHER a grounded field or isolated field, merely by grounding either field terminal and hooking your green wire to the remaining one. "Squareback" ONLY come in isolated field, where the older "roundback" (like yours) came in grounded field up through 69 and then in "isolated field" from 70 to ?? about 73. THESE ARE OFTEN INCORRECTLY NAMED "dual field". They do not have a "dual field." They are "isolated field" that is, "not" grounded

Also go over to MyMopar, and download a free shop manual. "Closest year" you can find. You may have to settle for Dodge/ vs Plymouth, etc. There are also aftermarket (3rd party) wiring diagrams there which can be easier to read but which sometimes leave out options and connectors. Both are very useful