I know which mine is because I went behind the counter and ordered the thing, then tested it when it came in. lol
Roundback vs. Squareback alternators?
- Thread starter halfafish
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Right, which is all I did to convert mine from round to square back. I just removed the hold down screw from one of the field blades, removed the fiber insulator washer and reinstalled the screw. Grounded and it charges great.
Ron816
Mopar forever
I went with Powermaster round back on my 68 works great, no issues
Its still a squareback. All you did was convert it to a grounded field alternator.
I know. That's what I said. lol It was NOT a square back originally. The car is a 64.
Yup that's what they call them. Who knows what they are actually capable of. Only way to know is to load test it at increasing rpm. I picked up a VAT40 last year but the meters aren't reading right. Not in a position to trouble shoot it.
Yea I had to buy an alt from Carquest some time back when the one I just had 'rebuilt' by a local guy crapped out an hour into a 6 hour drive home. All a crap shoot. The one from carquest later ended up needing a new stator. That may have been in part because I had to use it for charging a very low battery. Sucky situation where having the ammeter was very helpful. Anyway. If you have a squareback you can replace almost everything with basic tools and no soldering is needed.
Yes you did. I read what you wrote wrong. LOL.
cudamark
Well-Known Member
Years ago when I was replacing alternators in customers cars, I asked my local rebuilder about the differences in the alternators. He basically said he could change the output on any of them and generally made them the highest he could with the parts that were available at the time. He'd also supply whatever output you wanted if you had a preference. Most of the rebuilds you get come with small diameter double groove pulleys which is good for most street applications. On race cars or engines that will see high rpm use, the larger diameter pulleys will allow the alt to live longer. That reminds me....I need to go see if he's still doing that work as I need one freshened up for a resto.
I got one of them hand held carbon pile testers. I compared it to a friend's Snap On tester...basically a newer VAT40 and it was right on the money. Kinda surprised me. ....pleasantly. All I got it for was kinda a "go or no go" kinda deal but it seems to be really accurate.Yup that's what they call them. Who knows what they are actually capable of. Only way to know is to load test it at increasing rpm. I picked up a VAT40 last year but the meters aren't reading right. Not in a position to trouble shoot it.
Yea I had to buy an alt from Carquest some time back when the one I just had 'rebuilt' by a local guy crapped out an hour into a 6 hour drive home. All a crap shoot. The one from carquest later ended up needing a new stator. That may have been in part because I had to use it for charging a very low battery. Sucky situation where having the ammeter was very helpful. Anyway. If you have a squareback you can replace almost everything with basic tools and no soldering is needed.
Ok, I went back and re-read it just in case, cause it's usually me that's effin up. lol
What most guys fixin these old cars up really don't realize is, for the most part, unless you're puttin in large by huge electrical accessories like big stereos, power windows, seats, big fans, ignitions you can weld with and such......you will never need even a 60A alternator.
Yup.
Here's what I've measured on my '85 Grand? Wagoneer.
The Wagoneer similar electrical loads as a 70s A-body.
Ignition and field: 4 amps
Wiper, slow: 3 amps
Heater fan, Low: 4 amps, Med 5.5 amps, High 9.5 amps
Parking & instrument lights: 5.5 amps
Hazard lamps: 4 to 12 amps
Headlights, H4 /HB2 low beam (60 W): 9.2 amps
Power was supplied at 14.8 - 15 Volts
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Here is the test sheet from the square back iv the video in Post 12.
Remember the rpm listed is alt shaft rpm not engine rpm.
Use your pulley diameter ratio to determin the alt shaft rpm at your engine idle rpm
Remember the rpm listed is alt shaft rpm not engine rpm.
Use your pulley diameter ratio to determin the alt shaft rpm at your engine idle rpm
I have a 69 dart the alternator just went on, and the only one they had around here was a square back one. When you removed the washer, did you put the brush/spring back in? With just a bare hole if I take out the brush, spring, washer the screw is too long.
I'll add some meat to this - I have an alternator that looks that is the round back and napa gave me the square back even thou the picture on their site shows a round back. So I have zero background to know what to do to this squareback to make it fork for my dart. Not trying to throw a monkey into the wrench
but the car has MSD ignition dist, coil, and box.any help will be gratefully appreciated.
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Then cut some of the screw off or get a shorter one.
Thankyou Rusty....so as I understand it I take out the spring/bushing assembly and put the screw in the empty slot.
No. Take out the insulating fiber washer only. All you're doing is making sure that brush is grounded.
Airstream65
Well-Known Member
I’m going through this fiasco with my 67! I ve been trying to hook up the second field with a second wire.At first it was charging at 12.3v at alt and battery. I replaced the Mopar Performance blue race only VR with a stock electronic ignition VR and hooked new blue wire,now it’s slightly overcharging! Still trying to sort out botched wiring. I did not remove the insulator from the second field to try just a one wire like original.I have a 69 dart the alternator just went on, and the only one they had around here was a square back one. When you removed the washer, did you put the brush/spring back in? With just a bare hole if I take out the brush, spring, washer the screw is too long.
I'll add some meat to this - I have an alternator that looks that is the round back and napa gave me the square back even thou the picture on their site shows a round back. So I have zero background to know what to do to this squareback to make it fork for my dart. Not trying to throw a monkey into the wrench
any help will be gratefully appreciated.
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I tried that and it still isn't charging. That's the way its in the car now, and checking the battery as it's running its going down still. I couldn't get it above 12.12 at the battery at 3krpm, took it to OReillys auto and it failed the test.
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Airstream65
Well-Known Member
Hopefully that’s your problem, I took mine back twice to get tested and checked out good, but today I started it and one of the alt case bolts backed out(it’s stripped!), so, back to oreillys.
I don't know what else to tell you. All you do is ground one of the field tabs. It doesn't matter which. Then attach the field wire on the car to the other that's not grounded. Done. If you didn't put the brush back in, there's no way it'll ever charge. Was the old one charging? If not, you sure it was the alternator?
This looks like it was either set up to be grounded or someone didn't put the correct brush with terminal on it.
Normally if its set up with both brushes having insulated holders,run a wire to ground like I show in the thread Dana linked to.
Normally if its set up with both brushes having insulated holders,run a wire to ground like I show in the thread Dana linked to.
May need a metal washer or two. Or trim the brush holder insulation. The insulator is raised where the washer sits.
Got stuck years ago while traveling.
I got 3 rebuilds in a row with the terminal cut off, like that picture above. Finally found out from Napa, they were cut off intentionally so you couldn't connect to it. Single field only.
I got 3 rebuilds in a row with the terminal cut off, like that picture above. Finally found out from Napa, they were cut off intentionally so you couldn't connect to it. Single field only.
The picture above where the one terminal is circled is the one I removed that washer from because the other one matches with what I have on the roundback so I couldnt mess with it. On my picture of my roundback the grd terminal is like the circled one, and it has no washer in it either so by removing the washer from the squareback circled terminal (above) it was identical to the one I removed from the car.
The roundback in the car I had tested by O`Reilly auto and it failed. I put the Napa squareback in last night minus the washer on the circled terminal and it still isnt charging.
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