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
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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.
Mattax
Just the facts, ma'am
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.
Mattax
Just the facts, ma'am
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.
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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!
Mattax
Just the facts, ma'am
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.
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ChargerKG
Active Member
Hey Electricians, I just replaced the alternator in the '65 Dart with this cheapo from NAPA. Ad states it is 60 Amp. It is a round back 2 wire. I am running the original single wire set up with one field terminal grounded. This is not cutting it. New Pre-1970 VR from Standard Electric Made in USA. Electronic Ignition, Orange box.
So output fluctuates quite a bit. Sometimes up to 18 volts reading at battery when cold. As the VR warms up it settles down to 13.5 to 14 volts but still have wild swings of output, flickering dash lights. Driving around after hot, stock amperes gauge might show discharging for 30 seconds then back to positive. From what I have read Electronic Ignition should use the later Electronic VR with the 2 wire set up. I want to keep the Electronic Ignition and use of stock Amp gauge. Have read a lot of posts about this but nothing about such erratic behavior. Any suggestions are welcome.
So output fluctuates quite a bit. Sometimes up to 18 volts reading at battery when cold. As the VR warms up it settles down to 13.5 to 14 volts but still have wild swings of output, flickering dash lights. Driving around after hot, stock amperes gauge might show discharging for 30 seconds then back to positive. From what I have read Electronic Ignition should use the later Electronic VR with the 2 wire set up. I want to keep the Electronic Ignition and use of stock Amp gauge. Have read a lot of posts about this but nothing about such erratic behavior. Any suggestions are welcome.
Mattax
Just the facts, ma'am
The amp gage is only showing whether and how much the battery is charging or discharging.
With a transistorized version of the VR, there will be no noise from the points, so your ECU is not in danger.
The fluctuation is probably one or combination of several possibilities:
1. High current draw alternator rotor. Do a search for 'field current draw' Your new alternator's rotor may be 2 or 3 times higher than the factroy designed for. It may also make a stronger magnetic field that breaks down more slowly. I don't know for sure. But 7+ amps instead of 2-3 amps is a big difference if that's what's going on.
2. Alternator's 'turn on' rpm is higher than a factory alternator and pulley. new alt's usually come with new pulleys. if the diameter is larger, then the alternator turns more slowly at any given rpm. At slow idle this means it may not be turning fast enough to produce power, at the same time it's rotor may be sucking 7 amps from the battery.
3. Battery capacity is getting low.
Since you have the older style VR, measure the V right at the regulator's input. If its not the same as the V at the battery or at the alternator's output, then that's at least part of the problem. In other words if the Regulator is seeing 13 Volts because there is high resistance in the alternator's output connections and the alternator is actually producing 18 V, the VR doesn't know that. Ther voltage drop will get worse during high current demand. For example immediately after starting the battery will suck maybe 15-20 amps (look at the gage) for recharging. Once its done recharging, then its essentially zero amps.
With a transistorized version of the VR, there will be no noise from the points, so your ECU is not in danger.
The fluctuation is probably one or combination of several possibilities:
1. High current draw alternator rotor. Do a search for 'field current draw' Your new alternator's rotor may be 2 or 3 times higher than the factroy designed for. It may also make a stronger magnetic field that breaks down more slowly. I don't know for sure. But 7+ amps instead of 2-3 amps is a big difference if that's what's going on.
2. Alternator's 'turn on' rpm is higher than a factory alternator and pulley. new alt's usually come with new pulleys. if the diameter is larger, then the alternator turns more slowly at any given rpm. At slow idle this means it may not be turning fast enough to produce power, at the same time it's rotor may be sucking 7 amps from the battery.
3. Battery capacity is getting low.
Since you have the older style VR, measure the V right at the regulator's input. If its not the same as the V at the battery or at the alternator's output, then that's at least part of the problem. In other words if the Regulator is seeing 13 Volts because there is high resistance in the alternator's output connections and the alternator is actually producing 18 V, the VR doesn't know that. Ther voltage drop will get worse during high current demand. For example immediately after starting the battery will suck maybe 15-20 amps (look at the gage) for recharging. Once its done recharging, then its essentially zero amps.
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ChargerKG
Active Member
Thanks Mattax, Battery is great and pulley is stock diameter so I am going with your possibility #1. Will compare V at VR vs. Battery tonight. Man, those headlights are bright at 18V 
KG
KG
Hyper_pak
Old School Chrysler Fan
Flat 70 style VR?
That's lucky. I have not seen a round back reman alt in years.
Unless either part was used successfully with the old parts I would warranty return the VR, and if that did not work then the alt.
18v is a full fielded alternator suggests a VR issue and flickering (as in rapid flickering vs pulsing) could be a diode issue in the alt.
ChargerKG
Active Member
Maddax, So I should compare voltage at VR by inserting + probe of voltmeter into blue wire socket when disconnected? or touch probe to blue wire blade of VR when connected? or does it not matter? For Dana67Dart, After I changed the alternator the original VR was causing even more flickering but less wild fluctuations. The new VR is better with the exception of crazy voltage to battery for short periods once in a while. Since I added the Electronic Ignition I might as well go with a 1970 VR and see if that calms everything down.
Seems like the Alt might be the issue. If it's under warranty exchange it.
Also if you have a round back you may get not be able to convert it to a 70 up system.
The field has to be insulated from the alternator
ChargerKG
Active Member
The alternator is 1970 ready. Has two insulated field terminals. I have grounded one by securing the brush with a metal washer instead of the plastic one. That terminal has nothing connected to it. It would not charge until I grounded it there. Also there is consistently about a 1/2 of volt less at the VR which I have read is normal so I agree it is probably a bad diode in the alt. I will exchange it.
Mattax
Just the facts, ma'am
It makes a difference.
Voltage drops when electrons are trying to move through resistance.
The more electrons trying to get through, the more energy is lost.
When you disconnect the Regulator, no electrons are going to the alternator's rotor. Soooooo....
- Any resistance from the juntion at the ballast to the regulator has been removed.
- The alternator is no longer producing power. The voltage difference should be zero.
Voltage differences are used to identify resistance in path that electrons are flowing. So to use this method (voltage drop), it neccessary to know the path the electrons are flowing and the current (how many electrons are using that path).
new vs. old. It would help if we see the type of regulator it is. An original and many replacements are a electromechanical regulator. Very easyto see and diagnose, but a little noisy. This is not noise we should see. The decay of the electromagnetic field takes time, so output voltage doesn't change at the rate the points are changing the feed current.
To me this sounds like poor connections, or low battery or both. With a bad diode or open winding power output is lower at any given rpm than it normally would be. If you think its alternator, then its something loose there - maybe the output stud.
Could also be poor connection(s) in the circuit. We have no idea how the ECU was added in, or the condition of the original wiring.
And finally yes, I suspect any repalcement alternator these days, especially since they all have a claimed '60 amp' rating.
See my comments above.
Voltage difference depends on current flow.
But if you measured 18 Volts at the battery. 18 volts at the alternator, and 17.5 volts at the regulator. Then the regulator isn't controlling. But the measurements need to be done at the same conditions.
Mattax
Just the facts, ma'am
Let's fill in some typical numbers we'd expect in the example diagramed above.
Engine at fast idle, and the battery drawing about 20 amps.
The ammeter shows around 20 amps going to the battery.
We measure 14.3 Volts at the battery positive and 14.5 V at the alternator.
So there is a .2 Volt drop in the path from the alternator to the battery. That's not bad considering there 25 amps flowing in the R6 wire through the bulkhead and 20 amps along the rest of the path through the ammeter, the bulkhead, the fusible link, and the starter relay junction. Plus the ground return path to the alternator housing.
There is also a half volt drop to the regulator. Some of that (as much .2 V) could be where the 25 amps goes through the bulkhead on the R6 Wire. The rest could easily be in the key switch and its junctions, and the bulkhead connection for the run circuit.
Mattax
Just the facts, ma'am
While I'm rambling on about this, lets take the same example, with the same resistances and exchange the factory alternator with a 2.5 amp field current draw, for one that draws 7.5 amps.
V=IxR
Voltage drop to the regulator with the factory alternator drawing 2.5 amps and the ignition drawing 2.5 amps was 0.3 Volts
.3 V = 5 amps x Resistance
Resistance = 0.06 ohms
New alternator increases the current in the ignition circuit to 10 amps
V = 10 amps x 0.6 ohms
V = 0.6 Volts
So here's how that plays out on the diagram of a battery recharging at 20 amps.
This is just to illustrate the relationship between current and voltage drop caused by the resistances to that current.
Generally we'd expect the most voltage drop in the connection at the bulkhead with highest current flow. And in fact this one of the locations we often do find heat damage. But all of the connections are vulnerable, and those exposed to weather, and engine heat, as well as wear (key switch) can develop problems over 50 years.
V=IxR
Voltage drop to the regulator with the factory alternator drawing 2.5 amps and the ignition drawing 2.5 amps was 0.3 Volts
.3 V = 5 amps x Resistance
Resistance = 0.06 ohms
New alternator increases the current in the ignition circuit to 10 amps
V = 10 amps x 0.6 ohms
V = 0.6 Volts
So here's how that plays out on the diagram of a battery recharging at 20 amps.
This is just to illustrate the relationship between current and voltage drop caused by the resistances to that current.
Generally we'd expect the most voltage drop in the connection at the bulkhead with highest current flow. And in fact this one of the locations we often do find heat damage. But all of the connections are vulnerable, and those exposed to weather, and engine heat, as well as wear (key switch) can develop problems over 50 years.
ChargerKG
Active Member
The Dart turned 60 years old this month so the possibilities are endless. My electronic ignition install is fine and has worked well for a year. The issue started with this alternator so I do not think the cause is wiring. If it wasn't for the occasional 18V spikes I would not worry about it. Battery is fine. Battery getting 13.5 to 14.5V mostly. I'll drive it over to my NAPA store and ask if they will take it back. Before this one I tried one from O'reilly and could not get it to charge. So it is true, there is new junk on shelves. FYI the new VR is a Standard Ignition VR101 from O'reilly. Thanks for your explanations and advise. I will chime back in with the solve. KG
ChargerKG
Active Member
So embarrassing. VR was not grounded very well against firewall so I ran a wire from the casing to the Neg. battery post and things settled down a lot but not completely. Ammeter still not stable enough and would occasionally stay left of center on gauge for a minute then flick back to C side. I ended up returning the round back 60 amp alternator for a remanufactured square back 45 amp unit. Returned the mechanical VR and replaced with '70+ electronic VR. So Dart is now using both field terminals on alt and everything seems right. Steady gage, bright lights always, no flickering. A big improvement.
My electrician looked at the 12V wire to the alternator and was shocked how small the factory wire is. He said that size wire is good for 20 amps max. So I Googled it and AWG (American Wire Gauge) ratings and charts show a 60 amp current should use a #6 gauge wire. That is a 1/4" diameter of twisted copper strands under the insulation. So how are these small wires holding up?
Here are the parts I used:
NAPA Premium+ 2132009 alternator rated 45-50 amps
NAPA Proformer VR38SB voltage regulator
Charge!
My electrician looked at the 12V wire to the alternator and was shocked how small the factory wire is. He said that size wire is good for 20 amps max. So I Googled it and AWG (American Wire Gauge) ratings and charts show a 60 amp current should use a #6 gauge wire. That is a 1/4" diameter of twisted copper strands under the insulation. So how are these small wires holding up?
Here are the parts I used:
NAPA Premium+ 2132009 alternator rated 45-50 amps
NAPA Proformer VR38SB voltage regulator
Charge!
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