Grounding one alternator field?

[Hilljack68]

I just picked up a 100A Powermaster roundback alternator for my 68 Coronet. It's a dual-field, but I'm just using one. A couple of questions:

-Is the additional amperage going to play nice with my electro-mechanical regulator?

-Do I need to ground the other field to the case of the alternator (see below)?

Thanks in advance!

 

[dvw]

When using a double plug field one must be grounded. The modern replacements are available with updated internals for the old style regulators. Or just add one circuit and swap to the 71 and up regulator.
Doug

 

[Don Frelier]

The real danger is running it without a fully charged battery.
You pump a bunch of current through the bulkhead and ammeter.
If the battery is charged and you haven't added a bunch of heavy loads it should be OK.

 

[Hilljack68]

The real danger is running it without a fully charged battery.
You pump a bunch of current through the bulkhead and ammeter.
If the battery is charged and you haven't added a bunch of heavy loads it should be OK.

No, I don't have any additional load that the factory didn't have (no electric fans, etc). In fact, I bypassed the ammeter and swapped to a Dakota Digital gauge package.

 

[Hilljack68]

So if I do just use the one field, do I ground the second one to the case, as shown?

 

[Gold Rush]

You must ground the second terminal to get current flow through the field which is internally connected

 

[Cranky]

So if I do just use the one field, do I ground the second one to the case, as shown?

Since the engine is grounded (or it should be) and the alternator is attached to the engine, grounding to the case should be good. Most people don't ground their engines all that great and imo, the factory didn't do all that great of a job either so adding additional grounds to the block never hurts. And if you run grounds to the firewall, make sure you dig into the paint to make contact with metal!!

 

[Hilljack68]

Since the engine is grounded (or it should be) and the alternator is attached to the engine, grounding to the case should be good. Most people don't ground their engines all that great and imo, the factory didn't do all that great of a job either so adding additional grounds to the block never hurts. And if you run grounds to the firewall, make sure you dig into the paint to make contact with metal!!

Thanks Cranky; that's what I thought... just wanted to be sure. Yeah, the block is grounded. When I switched to an orange box a couple years ago, I was reminded of why we scrape the paint off to get better connections... doh!

 

[RJRENTON]

So if I do just use the one field, do I ground the second one to the case, as shown?

YES.......IT DOES NOT MATTER WHICH FIELD IS GROUNDED.....IMO, the old mechanical voltage regulator will work fine....the extra amperage produced by the alternator is made by the STATOR WINDINGS AND DIODES, the rotating field windings produce the magnetic field which is transformed to AC power and rectified (changed) to DC by the diodes.
BOB RENTON

 

[dvw]

YES.......IT DOES NOT MATTER WHICH FIELD IS GROUNDED.....IMO, the old mechanical voltage regulator will work fine....the extra amperage produced by the alternator is made by the STATOR WINDINGS AND DIODES, the rotating field windings produce the magnetic field which is transformed to AC power and rectified (changed) to DC by the diodes.
BOB RENTON

Explain this please. I've never had an issue grounding either terminal

Doug

 

[1 Wild R/T]

What people refer to as dual field is in fact a single field... The early design (69 & earlier) had one end of the field windings internally grounded & the field was energized by the regulator supplying 12v to the other end of the field winding.... Beginning in 1970 Chrysler stopped internally grounding the one end of the field winding & instead it was fed switched 12V so when the key if off the field is not energized but key on the 12v is always present & rather than pulsing the 12v to regulate the alternators output the regulator switches the ground... It's easier on the electronic components, creates less electrical noise & generally is a better design.... When engineers change stuff it's usually better... Unless it's to make the bean counters happy... Then it's just cheaper...

 

[RJRENTON]

Explain this please. I've never had an issue grounding either terminal

Doug

The alternator's rotating field windings are not polarity sensitive., therefore it does not matter which field terminal is positive (voltage source from the voltage regulator) and the other terminal is grounded. The voltage regulator provides the "variable" DC voltage (in the neighborhood of 0 - 6 to 8 volts ) to magnetize the rotating field windings. The higher the field voltage, the more the alternator's output voltage and current will be, limited to the impedance of the stator windings and diode capacity. The isolated field alternator circuit using the electronic voltage regulator is different, as the electronic voltage regulator supplies the variable voltage/current supply to the alternator's rotating field. I can explain further if interested.
BOB RENTON

 

[dvw]

The alternator's rotating field windings are not polarity sensitive., therefore it does not matter which field terminal is positive (voltage source from the voltage regulator) and the other terminal is grounded. The voltage regulator provides the "variable" DC voltage (in the neighborhood of 0 - 6 to 8 volts ) to magnetize the rotating field windings. The higher the field voltage, the more the alternator's output voltage and current will be, limited to the impedance of the stator windings and diode capacity. The isolated field alternator circuit using the electronic voltage regulator is different, as the electronic voltage regulator supplies the variable voltage/current supply to the alternator's rotating field. I can explain further if interested.
BOB RENTON

I missread your post. I thought it read it DID matter which I didn't understand.
Doug