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Discussion Starter · #1 ·
VMFers,

Please help me out with finding the right alternator for my needs. Currently the 66 A code has a stock alternator that is struggling to keep up with the electric fan and a sound system with subs. Also, I plan on adding air conditioning in the future so I'd need to future proof for that. I've done my due diligence and searched the forms but the waters are still murky with the different options. I think I'd like an 100amp 1g alternator and I don't want to mess with the stock ammeter. Is that even possible? If it is, would rebuilding the stock alternator be my best bet? I'm so confused. Thank you all again for your wisdom and help!!

Sincerely,

Corey
 

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Discussion Starter · #3 ·
Thanks for the reply GT. I'm not exactly sure how much power I'll actually need. I just want to make sure it's enough to power what's currently installed and an air conditioner in the near future. I've read that 1g or 3 wire alternators are actually better than 3g 1 wire alternators so I'm leaning toward that option. If what I've gathered is correct, 1g alts have an external regulator and 3g use an internal one that won't work with the ammeter. Am I correct in this assumption? Thanks again!
 

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67 coupe, 69 Sportsroof, 86 hatchback
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"I've read that 1g or 3 wire alternators are actually better than 3g 1 wire alternators"
I'm sorry, but where did you read THAT? If you don't mind me asking.
 

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To get that output from a 1G alternator you'll need to go from the original small-case to a large-case unit, and change the brackets, accordingly as they're an inch wider. You'll be able to retain ALL your existing wiring with the exception of the output wire that runs from the alternator to the battery-side of the starter solenoid. You'll need a #6AWG wire to handle a 100 amp current. I can't remember for sure, but something in the back of my mind tells me that the existing wire is a 10AWG....

The 1G alternators aren't necessarily "better", nor are 1-wire alternators, but each type has its advantages. Using a 1G lets you retain the majority of your existing wiring, including your ammeter. Using a 3G will provide you with more charging amps, especially off idle. One-wire alternators can be harder to excite and may require an initial throttle "blip" to start them charging, but WILL require modification of your harness and a different approach to retaining your ammeter.

The practical thing to do is to add up the maximum amp draw that you could potentially experience for an extended period which would, otherwise, discharge the battery, and size your alternator to that need.
 

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Just some guy
67 coupe, 69 Sportsroof, 86 hatchback
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Speaking of those big case 1G's, I used to be all about swapping to big case 1G 100 amp alternators back before I heard of 3G swaps. (OK fine, back before 3G's even existed.) I NEVER got the charging performance I wanted at lower RPM's until I switched a 3G. Been sold on 3G's ever since. The big downside I see with them is they look far from stock in a car that is "supposed" to have a 1G.
And by the way, there was an interesting thread about using a ammeter with a 3G not long ago. Here-
http://forums.vintage-mustang.com/vintage-mustang-forum/910746-3g-alt-upgrade-keep-ammeter.html
 

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Discussion Starter · #7 ·
"I've read that 1g or 3 wire alternators are actually better than 3g 1 wire alternators"
I'm sorry, but where did you read THAT? If you don't mind me asking.
I think I may have misunderstood that 3g alternators could also be 3 wire. My previous notion was based off 1vs3 wire comparison previously linked here Catalog
 

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Discussion Starter · #8 ·
Speaking of those big case 1G's, I used to be all about swapping to big case 1G 100 amp alternators back before I heard of 3G swaps. (OK fine, back before 3G's even existed.) I NEVER got the charging performance I wanted at lower RPM's until I switched a 3G. Been sold on 3G's ever since. The big downside I see with them is they look far from stock in a car that is "supposed" to have a 1G.
And by the way, there was an interesting thread about using a ammeter with a 3G not long ago. Here-
http://forums.vintage-mustang.com/vintage-mustang-forum/910746-3g-alt-upgrade-keep-ammeter.html

I read that string as well Gypsy, thank you. This subject is a little bit more clear now.

Bartl, as always your insight is much appreciated.

So, please let me know if I have this right. With a 100amp alternator I'd have to modify the bracketing regardless if it's a 1 or 3G. 1g can be utilized without wiring modification (except for the output wire) and retains the use of the ammeter. 3G would require wire modification or a conversion kit and ammeter use would require re-wiring making the adoption of a voltmeter more attractive.


Again, thank you both for your help. I'm starting to feel like I'm nuking this.....:loco:
 

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Yeah, that's about the gist of it. Consider yourself lucky that you have a working ammeter... most of them quit before leaving the dealership.
 

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Discussion Starter · #10 ·
Yeah, that's about the gist of it. Consider yourself lucky that you have a working ammeter... most of them quit before leaving the dealership.
Crap, now I'm starting to wonder if the ammeter really works. The needle occasionally will tick right or left but no more than 25% in either direction. Most of the time it rests at dead center.
 

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pa-performance.com sells a 3G 95A small case that is about the same size as a 1G and will bolt in to your existing brackets. It only requires an upgraded power wire, and pa-performance sells that also. My project Mustang will have AC, power windows, and electric fans and all it needs is the 95 amp model.
Here's a chart from their website showing various alternators output.
PA Performance- You only buy quality once!- 877-471-8010
 

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Just some guy
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J beat me to it. A 95 amp is a physical direct bolt-in and will do the job just fine. Stock in , I believe, a 1994 Mustang GT? Somebody will have to confirm that though. I prefer the larger 130 amp overkill 1996 3.8 Mustang versions myself. But you have to change/modify the brackets to fit those, admittedly a pain to do.
 

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If you give them a call, he may suggest any items that you have overlooked. Be sure and tell them what type of pulley you need, V belt or serp.
 

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Crap, now I'm starting to wonder if the ammeter really works...
From another thread:
"The problem with these post-'65 ammeters is that they weren't durable enough for the demand. Most burned up and failed early in their service life..." Ford Mustang Instrument Panel Troubleshooting - Mustang Monthly
http://forums.vintage-mustang.com/vintage-mustang-forum/910746-3g-alt-upgrade-keep-ammeter.html

That's why some folks do an ammeter-to-voltmeter conversion. Like this one from Rocketman (scroll down): Rocketman's Classic Cougar Innovations

Or consider a "temporary" alternative. Lots of cigarette lighter gauges, like this: http://www.amazon.com/HappyPrimeDay...9&sr=1-2&keywords=voltmeter+cigarette+lighter

Or a cheap under-dash add-on:
 

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Discussion Starter · #17 ·
Perfect, I have my plan of attack all set. Thanks everyone, VMF is the best!
 

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AllCoupedUp - I looked at those PA kits and all they do is swap a box and bypass a few wires. These guys helped me with my post that V8 Junkie referenced because I was hoping to do a 3G upgrade and keep the original looking gauges.

Give this blog post a read to find out if 95, 100, or 130 amps is going to be enough: How to Choose an Alternator - OnAllCylinders

When it comes to 1 wire or 3 wire, 1G or 3G i know I have been down that road. I have finally decided on a 3G 130 amp upgrade with a Rocketman Amp to Volt meter conversion. Going to take out the old wires and put in new in the charging system.
 

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AllCoupedUp - I looked at those PA kits and all they do is swap a box and bypass a few wires. These guys helped me with my post that V8 Junkie referenced because I was hoping to do a 3G upgrade and keep the original looking gauges.

Give this blog post a read to find out if 95, 100, or 130 amps is going to be enough: How to Choose an Alternator - OnAllCylinders

When it comes to 1 wire or 3 wire, 1G or 3G i know I have been down that road. I have finally decided on a 3G 130 amp upgrade with a Rocketman Amp to Volt meter conversion. Going to take out the old wires and put in new in the charging system.
The problem with that chart is they list all the amp draw of the various systems, and nowhere do they explain that some of the higher amp draws are intermittent such as the seats and power windows and a few others. It's nice to know what all the accessories consume but irrelevant in the normal day to day operation.
 
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