alt upgrade 1968 to 1970 two field

[Mike Browne]

Picked up a two field alt and regulator. The new alt has a smaller pully 2 1/2" OD old alt and not sure if it had the correct pulley was 3 1/4" OD. This will spin the new alt faster. Is this OK? This is for my 1968 300 with A/C. Lost alt on the way back form car show Saturday. Cut belts off and made it home. About 20 miles from home. Turned out to be a good day nice car show.

 

[LocuMob]

You can just install the dual field alternator, and ground one of the field wires to the case with a jumper wire. Or go and add the extra wire of you'd like.

 

[Davea Lux]

Picked up a two field alt and regulator. The new alt has a smaller pully 2 1/2" OD old alt and not sure if it had the correct pulley was 3 1/4" OD. This will spin the new alt faster. Is this OK? This is for my 1968 300 with A/C. Lost alt on the way back form car show Saturday. Cut belts of and made it home. About 20 miles from home. Turned out to be a good day nice car show.

The smaller pulley will not hurt anything either but you will need to compensate with slightly shorter belts to maintain the proper adjustment as using stock belts, you will loose about half of the normal adjustment.

Dave

 

[Trace 300 Hurst]

I know it's become common to use the terminology, but it's not a DUAL FIELD alternator. There's only one field in that alternator. It's simply has "two" connections instead of one due to the electronic voltage regulator/wiring system.

 

[Trace 300 Hurst]

I'm gonna start calling them "DUEL FIELD" alternators.

 

[Trace 300 Hurst]

Turned out to be a good day nice car show.

Every day is a nice day in Napa!!

 

[mr. fix it]

You can just install the dual field alternator, and ground one of the field wires to the case with a jumper wire. Or go and add the extra wire of you'd like.

What does grounding the extra field connection do?
I thought that you had no choice but to run the 2nd wire and change the regulator...

 

[Davea Lux]

What does grounding the extra field connection do?
I thought that you had no choice but to run the 2nd wire and change the regulator...

The second wire goes to ground to complete the field circuit. It does not matter where it goes to ground. Unless you plan to convert to electronic ignition, you do not have to have the electronic regulator.

Dave

 

[LocuMob]

What does grounding the extra field connection do?
I thought that you had no choice but to run the 2nd wire and change the regulator...

It made it so I could run the stock wiring in my Polara 500 without doing anything else, and have an alternator. I didn't have any round back units (I see t them away for free, then needed them!) so I used a square back, added the wire and I was done.

 

[Mike Browne]

Every day is a nice day in Napa!!

Thank you. nice place to live. never to hot or cold. and no rusting car.

 

[mr. fix it]

The second wire goes to ground to complete the field circuit. It does not matter where it goes to ground. Unless you plan to convert to electronic ignition, you do not have to have the electronic regulator.

Dave

Ok thanks for the explanation.
I have a dual field and have not converted to the newer electronic regulator other than using an OEM looking electronic reg.

 

[Big_John]

Ok thanks for the explanation.
I have a dual field and have not converted to the newer electronic regulator other than using an OEM looking electronic reg.

The real difference is that the older versions control the field by turning the positive on and off. The newer style controls the field by turning the negative on and off.

The electronic regulator does the job better by turning it on and off faster and that gives a "smoother" ( for lack of a better word) output.

With an electronic regulator now readily available for the earlier style alternator, there's no reason or improvement by fitting the newer style regulator

The differences of the alternator is the earlier version is internally grounded. The later version, incorrectly called "duel field" is not internally grounded . The correct term is "isolated field". By grounding one terminal, you are converting the isolated field to an internally grounded field

 

[Davea Lux]

The second wire goes to ground to complete the field circuit. It does not matter where it goes to ground.

Dave

The real difference is that the older versions control the field by turning the positive on and off. The newer style controls the field by turning the negative on and off.

The electronic regulator does the job better by turning it on and off faster and that gives a "smoother" ( for lack of a better word) output.

With an electronic regulator now readily available for the earlier style alternator, there's no reason or improvement by fitting the newer style regulator

The differences of the alternator is the earlier version is internally grounded. The later version, incorrectly called "duel field" is not internally grounded . The correct term is "isolated field". By grounding one terminal, you are converting the isolated field to an internally grounded field

Chrysler was anticipating the transition to electronic ignition. The electronic regulator was a means to an end to control voltage spikes from points opening and closing rather slowly. The electronic units as noted did this function much more rapidly and kept the power to electronics steady to help prevent damage. The isolated field alternators also had improved insulation to the field winding to help control static.

Dave

 

[mr. fix it]

The real difference is that the older versions control the field by turning the positive on and off. The newer style controls the field by turning the negative on and off.

The electronic regulator does the job better by turning it on and off faster and that gives a "smoother" ( for lack of a better word) output.

With an electronic regulator now readily available for the earlier style alternator, there's no reason or improvement by fitting the newer style regulator

The differences of the alternator is the earlier version is internally grounded. The later version, incorrectly called "duel field" is not internally grounded . The correct term is "isolated field". By grounding one terminal, you are converting the isolated field to an internally grounded field

Will it make any difference on charging when idling?

 

[Trace 300 Hurst]

Chrysler was anticipating the transition to electronic ignition. The electronic regulator was a means to an end to control voltage spikes from points opening and closing rather slowly. The electronic units as noted did this function much more rapidly and kept the power to electronics steady to help prevent damage. The isolated field alternators also had improved insulation to the field winding to help control static.

Clear, historical, outstanding explanation!

Duel, dual.....ISOLATED!

 

[Big_John]

Will it make any difference on charging when idling?

Low charging when idling is an ongoing problem with old Mopars... No doubt about it.

Here's what happens... Some guy will have that problem and do the "upgrade" to an isolated field alternator and an electronic regulator. Their problem stops, so they figure that's the way to fix it. They tell everyone on the forums, Facebook and all their buddies that the "dual field alternators is the cure".

What has really happened is they swapped out a low output alternator (bad diode etc.) and/or a bad regulator and/or bad wiring for new components... and what they aren't telling you is they now have a 60-100 amp alternator rather than the stock output version. They'll also do the "Mad" or "Nacho" ammeter bypass and declare they saved the world from another Chicago fire. No diagnosis of the original problem etc.

Now, there's nothing wrong with doing this "upgrade". People will argue all day that it is the way to go, but whatever.

It comes down to everything has to work. The alternator has to be spinning at the right speed, the regulator has to be turning the field off and on and making the alternator charge the battery. The wiring has to be good, including the connections at the firewall and at the ammeter, the battery cables tight and clean. A good battery etc.

IMHO, a good and sensible upgrade with a pre 1970 car is an electronic regulator. That's really all it needs. Then it's all preventive maintenance. Clean the battery cables and get rid of those problem causing "temporary" battery terminals that everyone loves to use. Clean the spade terminals at the firewall and slide under the dash and make sure the ammeter terminals are tight. This is the way my '65 Barracuda is set up.

My '70 Chrysler, on the other hand, has some added electronic load and for that, I've done the "Nacho" bypass... Of course, I didn't know that it had a name at the time, but here it is for those interested. Some considerations about the charging and wiring upgrade and your worries about

Start adding stuff like EFI, electric fans, audio amplifiers etc. and that's another story.

 

[jct]

I combined the Mad and Nacho

 

[Trace 300 Hurst]

Thank you. nice place to live. never to hot or cold. and no rusting car.

Contemplating another trip there, maybe next spring, maybe harvest season next year. As you mentioned, most any time is a good time.