Correct alternator for 1968 charger 440 HELP

[Tim Lyons]

I purchased a new alternator for my 1968 dodge charger 440. The alternators look the same but it looks like the new one has an extra field tab. Is this the incorrect alternator or do I just use the 1. Any help greatly appreciated.

 

[Nacho-RT74]

The new one is based on 70/71 housing, when Mopar went dual field alt still being roundback. They were built with both brushed isolated from case where earliers got one brush attached straight to the alt case ( grounded ). I guess the extra field tab mounted on an isolator is already grounded somehow ( maybe a metalic washer down the screw ) to make it work as earliers, with a grounded brush. So don't worry about it and wire the alt as you had with the old one

 

[R413]

Use your meter and see if one of the tabs is grounded to the case. If it is cut off the Tab terminal so a wire cannot be plugged on to the grounded one.

 

[RJRENTON]

Use the alternator as is, using the single field connection terminal, located in the shrouded area (where the mounting pivot bolt passes thru). Ignore the other brush (ground brush).
BOB RENTON

 

[Tim Lyons]

Hey thanks guys!

 

[dadsbee]

Hey thanks guys!

Just make sure you follow R413's advise and make sure only one of the connection tabs is grounded to the case (and not both) or we'll have another "why did my wiring melt" threads going. Then clip that tab so it's never mistakenly used...

 

[Tim Lyons]

I ohm tested both tabs and they both seem to be grounded to the case. Both have brushes under them also?

 

[dadsbee]

To work one tab should be grounded (zero ohms) and the other should be showing the resistance of the field winding between case and tab. Why I highly seconded the testing advise after a member burnt up his wiring TWICE last week due to exactly this..

 

[70sixpkrt]

How do you test an alternator?

 

[1 Wild R/T]

How do you test an alternator?

Are you wanting to test the output? Or test for a grounded field winding like the O/P is needing to do?

 

[70sixpkrt]

Are you wanting to test the output? Or test for a grounded field winding like the O/P is needing to do?

Sorry for side track. Test the alternator in the car.

 

[RJRENTON]

Sorry for side track. Test the alternator in the car.

Yes...the alternator must be tested in the car (driven at a specific RPM per FSM procedures) with specific field voltage applied. Maximum amperage output is determined by the stator windings (wire size and number of windings per phase) and diode capacity. Other electrical tests, (ohms/phase & ohms to ground of the stator windings, ohms to ground rotor, rotor resistance, ohms to ground of the brush holders, forward & reverse resistance readings of the diodes) can be performed with the alternator on the bench and disassembled. Specific as to what you want tested.
BOB RENTON