64 Plymouth Fury Alternator Question

[JJordan1173]

Hello All,

Doing my first alternator change. Never done one before on these old mopars. Current setup is a single pulley alternator with no belt tensioner. I am not able to find the exact stock one and I am considering buying new from rockauto. The amp rating I am seeing on new is 60amps. Will that work as a suitable replacement? Thanks!

1964 PLYMOUTH FURY 3.7L 225cid L6 Alternator / Generator | RockAuto

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[Darter6]

Yes. Looking at the photos it IS a single field pre 1970 alternator.
Single Belt FVP 7000112 ? Is that the one you are looking at ?
Try to get the single pulley if you can. Possible with a 2 belt pulley you may have to do some shimming for belt alignment.

 

[JJordan1173]

Yes. Looking at the photos it IS a single field pre 1970 alternator.
Single Belt FVP 7000112 ? Is that the one you are looking at ?

Yes! Great. I guess it IS a reman. Thanks

 

[JJordan1173]

Yes. Looking at the photos it IS a single field pre 1970 alternator.
Single Belt FVP 7000112 ? Is that the one you are looking at ?
Try to get the single pulley if you can. Possible with a 2 belt pulley you may have to do some shimming for belt alignment.

I have battery voltage at the positive terminal of the alternator however when I have the key in the on position I do not have any voltage at the field wire from the external voltage regulator. Does this indicate that it is just my voltage regulator? Hoping so because they are much cheaper than a new alternator.
Thanks

 

[Darter6]

Dang if I know. So you have used the volt meter on the battery while the engine is running and you have no more than 12.6 volts? Should be at least 13.8 volts to charge the battery.So field side has nothing when the key is on.Is there voltage at the IGN side ? that is the spade terminal that pushes on. That power comes from the key.You may have a ignition switch problem if nothing is there.
Not that this helps
Old trick to see if your charging system in a Mopar is working.
Take a flat blade screwdriver and touch it to the back of the alternator where the center of the rear bearing is.
you should feel it stick as it is magnetic. Not strong but you will feel it. But sounds like you have a meter to measure actual voltage.
I don't have a 64 wire diagram so I can't help with that.
Go to My Mopar web site and look up the wiring diagram for your car.

 

[JJordan1173]

Dang if I know. So you have used the volt meter on the battery while the engine is running and you have no more than 12.6 volts? Should be at least 13.8 volts to charge the battery.So field side has nothing when the key is on.Is there voltage at the IGN side ? that is the spade terminal that pushes on. That power comes from the key.You may have a ignition switch problem if nothing is there.
Not that this helps
Old trick to see if your charging system in a Mopar is working.
Take a flat blade screwdriver and touch it to the back of the alternator where the center of the rear bearing is.
you should feel it stick as it is magnetic. Not strong but you will feel it. But sounds like you have a meter to measure actual voltage.
I don't have a 64 wire diagram so I can't help with that.
Go to My Mopar web site and look up the wiring diagram for your car.

Yeah I tested with a meter and I have battery voltage on the ignition side of the voltage regulator and no power at the field terminal on the alternator when key is in on position. I am no expert either but it leads me to believe it is a faulty voltage regulator.
Thanks for the tip. I am try that tomorrow!

 

[RJRENTON]

It is very likely that the original alternator was EITHER: 37 amp or 46 amp single field round back design. Dual sheave units (46 amp) were usually used on A/C cars; single sheave units (37 amp) were used on everything else except police package then the alternator was a Leece-Neville unit (physically different in size). Both Mopar units used a mechanical voltage regulator firewall mounted.
Changing to a newer "rebuilt" 60 amp unit will work but MAY cause wiring issues (bulkhead connrctors) and future wiring problems. WHAT IS WRONG WITH YOUR ORIGIONAL ALTERNATOR? IS IT NOT WORKING OR MAKING NOISE? It is rebuild-able for less $$ than a 60 amp auto parts store replacement......just my opinion of course....remember...it's only origional ONCE....if you change, keep the original unit
BOB RENTON

 

[R413]

Try starting the car to check the charging system.

Check voltage at the battery at 1200 rpm, not idle.

Do this and tell us what you have. 12.X volts bad,
13.5 to 14.5 volts good.

 

[JJordan1173]

Try starting the car to check the charging system.

Check voltage at the battery at 1200 rpm, not idle.

Do this and tell us what you have. 12.X volts bad,
13.5 to 14.5 volts good.

It remains at 12.4. when the rpms increase.

 

[RJRENTON]

It remains at 12.4. when the rpms increase.

It is very likely that the mechanical voltage regulator has failed. There are new electronic voltage regulator replacements that resemble the origional unit and do not require any wiring changes or additions. The cost is approximately $25.00 (on line suppliers). If that does not fix the low voltage issue, it's possible that the alternator has an open diode. Mopar alternators are a three phase full wave design and if a diode has failed open, the voltage will be low and the amperage will be half the rated output. Diodes are easy to test and easy to replace.
BOB RENTON

 

[JJordan1173]

It is very likely that the mechanical voltage regulator has failed. There are new electronic voltage regulator replacements that resemble the origional unit and do not require any wiring changes or additions. The cost is approximately $25.00 (on line suppliers). If that does not fix the low voltage issue, it's possible that the alternator has an open diode. Mopar alternators are a three phase full wave design and if a diode has failed open, the voltage will be low and the amperage will be half the rated output. Diodes are easy to test and easy to replace.
BOB RENTON

I grounded the field wiring coming from the voltage regulator at the negative post of the battery via a jumper wire and the alternator still failed to charge. My understanding is that the voltage regulator is essentially a switch that "opens" or creates a ground when the battery power drops below a certain threshold. This ground therefore completes the circuit on the alternator grounding it and therefore allowing it to charge the battery. I replicated this grounding to the alternator and it failed to respond. I have since ordered a replacement alternator. Hopefully this will solve the issue.

 

[JJordan1173]

It is very likely that the mechanical voltage regulator has failed. There are new electronic voltage regulator replacements that resemble the origional unit and do not require any wiring changes or additions. The cost is approximately $25.00 (on line suppliers). If that does not fix the low voltage issue, it's possible that the alternator has an open diode. Mopar alternators are a three phase full wave design and if a diode has failed open, the voltage will be low and the amperage will be half the rated output. Diodes are easy to test and easy to replace.
BOB RENTON

Bob, that being said I'm interested to know about rebuilding an alternator if I can do it at home. I can always send the new alternator back whenever it arrives in the mail. Thanks

 

[RJRENTON]

I grounded the field wiring coming from the voltage regulator at the negative post of the battery via a jumper wire and the alternator still failed to charge. My understanding is that the voltage regulator is essentially a switch that "opens" or creates a ground when the battery power drops below a certain threshold. This ground therefore completes the circuit on the alternator grounding it and therefore allowing it to charge the battery. I replicated this grounding to the alternator and it failed to respond. I have since ordered a replacement alternator. Hopefully this will solve the issue.

Your assumption is PARTIALLY correct. The mechanical voltage regulator is a switch that applies 12 volts (from the battery thru the ignition switch) thru the regulator to the alternator's rotating field windings. The voltage regulator supplies EITHER 12 volts (battery voltage) or approximately 6 volts (via a resistor under the regulator) or zero (0) volts to the alternator's rotating field. Its monitoring the battery's voltage to try and maintain approximately 14.5 volts at the battery connections, measured at the battery. The old mechanical voltage regulator internal contacts can be worn from being turned on/off 1000s of time.
I suggest you obtain a copy of the Factory Shop Manual (FSM) for your year and model car.....on line at zero cost. It explains all about the car and accessories. PM me to discuss rebuilding the alternator or anything about your car.....i'll help if I can. To test the alternator, disconnect the green.wire on the alternator and run a TEMPORARY jumper from the battery's plus terminal to the alternator's field terminal, which furnishes full voltage to the alternator's rotating field, causing it to charge at max. If it does charge with the engine running, then replace the VOLTAGE REGULATOR.
BOB RENTON

 

[JJordan1173]

Your assumption is PARTIALLY correct. The mechanical voltage regulator is a switch that applies 12 volts (from the battery thru the ignition switch) thru the regulator to the alternator's rotating field windings. The voltage regulator supplies EITHER 12 volts (battery voltage) or approximately 6 volts (via a resistor under the regulator) or zero (0) volts to the alternator's rotating field. Its monitoring the battery's voltage to try and maintain approximately 14.5 volts at the battery connections, measured at the battery. The old mechanical voltage regulator internal contacts can be worn from being turned on/off 1000s of time.
I suggest you obtain a copy of the Factory Shop Manual (FSM) for your year and model car.....on line at zero cost. It explains all about the car and accessories. PM me to discuss rebuilding the alternator or anything about your car.....i'll help if I can. To test the alternator, disconnect the green.wire on the alternator and run a TEMPORARY jumper from the battery's plus terminal to the alternator's field terminal, which furnishes full voltage to the alternator's rotating field, causing it to charge at max. If it does charge with the engine running, then replace the VOLTAGE REGULATOR.
BOB RENTON

Just did the test and you were right! Battery began charging. I will return the new alterbator and get a new voltage regulator. Are those ones on amazon any good? Or should I spring for the Blue Streak one? It's around $50. Thanks again Bob. And yes I picked up a shop manual a while back I should have read it more carefully.

 

[RJRENTON]

Just did the test and you were right! Battery began charging. I will return the new alterbator and get a new voltage regulator. Are those ones on amazon any good? Or should I spring for the Blue Streak one? It's around $50. Thanks again Bob. And yes I picked up a shop manual a while back I should have read it more carefully.

I'm glad youve found your problem. As far as the Amazon offerings vs Standard Motor Products BLUE STREAK goes.....it would be my preference to use Blue Streak for a few more $$, but it's your choice but if cost is a consideration, which offering has a better warranty? REMEMBER to remove your test jumper wire AND DISCONNECT THE BATTERY b4 changing the regulator. Anyway......be careful in your journey and endeavors......PS....the old mechanical voltage regulator has two internal fuse wires...usually one eill fail when the points stick together....remove the cover of the old unit to see the internal fuses wires....if you're curious.....regards......
BOB RENTON