Hi everyone, can you swap out a round back 2 wire alt for a 2 wire square back alt on a 64 barracuda without any modifications? Thanks for info
Round back to square back alt
- Thread starter Cuda 1964
- Start date
-
67Dart273
Well-Known Member
Just ground one brush and bolt it on, or take that opportunity to convert to a 70/ later VR which only requires one more wire
Some claim that some of the squarebacks draw more field current, but I've not had trouble with them thataway
Some claim that some of the squarebacks draw more field current, but I've not had trouble with them thataway
Just to be sure....
You're talking about the original single field wire "round back" alternator
And you want to replace it with a 2 field wire "square back" alternator.
The original round back alt was a two wire could have been a single field which was on a 273 64 Cuda would like to replace it with a powermaster 17519 two wire square back
Just some terminology....
2 wires on the round back means the charge wire and the single field wire.
Square back alternators have 3 wires, 2 field and one charge wire.
Some square back alternators have been modified by the manufacturer / remanufactured to internally ground one of the field wires so they can be used on an application that calls for a single field wire.
2 wires on the round back means the charge wire and the single field wire.
Square back alternators have 3 wires, 2 field and one charge wire.
Some square back alternators have been modified by the manufacturer / remanufactured to internally ground one of the field wires so they can be used on an application that calls for a single field wire.
I suspect anything from Powermaster will have draw more field current. Likely it will be 2 x the current the regulator was inteded to handle. Also if there are any problems or weaknesses in the circuits, this will magnify them.
In some applications, the size of the squareback will limit the travel for tensioning the bolt, and a shorter belt will need to be used. Not to mention, the increased output of the Powermaster unit may be more than the old 64 wiring can handle.
Output depends on demand. So the only increase in demand will be, or could be, the field current. On the other hand, at idle speeds, that increase can be the difference between having enough power to run the headlights, wipers, and brake lights without dipping into the battery.
Last edited:
67Dart273
Well-Known Member
Another possibility is, that even if the field current allegation is correct, (and assuming one stays with the early VR) these modern replacement VRs have a pass transistor that may or may not be heavier duty !!! than the old electro-mechanical ones. THAT could go either way.
ANOTHER reason for "adding one more wire" and converting to the flat, 70 and later VR
ANOTHER reason for "adding one more wire" and converting to the flat, 70 and later VR
That's a mouth full, and the biggest problem with our old undersized wiring.
Add brighter headlights, stereo, electric fans, etc and zap/smoke!
Old underpowered alternator will just max out at 40 or so amps and things might just get hot!
It's not a problem until someone inadvertently adds load like electric fans. Or adds load to wires and connections that can't handle it
Even then, its not a zap! poof situation, more typically your slow burn (melt) scenario.
The alternator won't care other than it too may get hot from running at near maximum. The battery has a tremendous capacity and will cover for a while.
Lets go over the loads.
Here's what I've measured on my '85 AMC Jeep SJ (with Delco 12SI alternator so field current is internal)
The Delco alternator was rated 74 amps or later 92 amps. It only put out 27.4 amps. Why?
Because that's all the loads that were turned on or connected.
A 64 Barracuda will have about 2.5 amps for the ignition and about the same for the field. Lets call it 5 amps
Headlights will be about the same, 9 amps. A little less if using the original lamps, or the 35 W low beam halogens.
Parking and instrument lights will be less since it has no side markers. lets call it 5 amps for simplicity.
Heater fan will probably be the same or less. Lets call it 9 amps.
Total current needed driving on a cold night, 27 amps.
Well within the capacity of a '34 amp' alternator at high idle or driving down the road.
The one load not listed is battery recharging. If the battery wants 10 amps (such as after starting), then the '34 amp' alternator will not be able to do that at slow idle and run all the stuff listed above. I don't have slow idle measurements for maximum power capacity for any unmolested Chrysler alternator of this period. But it is not uncommon for A-body owners to comment on the fact that the ammeter will flick slightly toward battery discharge when at a stop light at night, especially with wipers or heater fan running. And yes rear brake lights add a few amps to the load.
Last edited:
-
