Hi! I have a '71 Mav, 200 engine. I took the car to a professional mechanic to check various things, including the alternator. He said it was under-powered, which I suspected. I'm considering getting a Motorcraft unit but there are a couple different ones available with different amp ratings. The car doesn’t have AC. Which amp rating should I get? Is there a higher amp rating Voltage Regulator I should also get? Thank you! Bye, Daniel
My original alternator with V-8 and A/C was a 55 amp. Get the highest output alternator you can find (unless you're just going for original). If you do upgrade to more than 75 amps, you'll need to use a larger gauge output wire. The voltage regulator regulates voltage, not amps...
Stock the 55A was the most available with A/C, without 42A was std. Unless you are adding large sound system, electric fans, etc the 42A is fine, my 428CJ still spins one.
To be fair the guy who advised you is correct. However one thing many over look is old wiring with high resistance. In essence it will cause similar issues. Plus it will cause repeat alternator and starter failures. Along with other system components. I would advise doing voltage drop tests on pertinent systems and sub systems. Best Regards, Rick
My 3G is rated at 150 amps. Just in case you decide to add stuff later. Adding LED lighting takes a lot of the load off.
Back in day 61A were highest, may be modern replacements of 70A. In late '70s/early '80s there were 100A that used external regulator. Problem is they are physically larger than orig, won't fit most brackets. Think I still have one, if so I'll shoot a pict. Having parted numerous different Fords, I've always picked one from stash & rebuilt it myself. Brush & bearings were $6-8(yeah those days are gone, though I still have a rebuild kit on hand). Only ones I remember purchasing rebuilt/new were a 2G for the long gone '86 Grand Marquis & a 3G for the '98. Within a month, blew up first replacement 3G. Crown Vic Cop 'puter in that car allows higher transmission shift points than civvy 'puter.
I went all LED on exterior lights. I did add a 2 stage elect fan. I have it on lower stage now. May have to move it to higher stage when I start driving it. Thats why Im worried about amps.
Put in a Volvo 2-speed controller on it then it'll start out on low and go high if you need. When it starts on low and then goes high you won't get that big current surge as when you go high from a dead start. https://www.ebay.com/itm/124902118496?epid=1739696149&hash=item1d14bf1460:g:vlAAAOSwH-daH01M
Since they are using a ground trigger switch , the purple wire feeds 12V to the + side of the relay 86(right) from the relay 87a(left) when car is cool. 87a is normally closed. This is because 86 (left) is shorted to 30(left) which is Bat+ via the brown wire, thus coming out 87a(left). When the car gets hi temp hot. 12V purple is switch off , killing relay right. Its kinda weird set up, but I assume it because the low temp switch never shuts off at high temp.
Back when I did the Mav copcar, charging amps became a major problem due to the emergency lights, etc. I got a custom 100 amp alternator with internal regulator and converted the car to one wire. It's actually a very simple conversion and the company included everything I needed along with easy to read instructions. My car was factory a/c and that prohibited using a number of other alternators due to their larger case size. Thus, why I had little choice but going custom but it is a viable alternative for your concerns. They're not as expensive as you might think and I never had issues with the conversion also considering I did not replace or upgrade any of the wiring other than the main to the alternator that needed changed for the conversion. Just putting an option out there.
That's no kidding. Long ago I had a 1974 LTD that would go a few months without any issues. Then out of nowhere every electrical part on the car would start failing without explanation. Alternators, starters, starter solenoids, voltage regulators, and more. Sometimes the same part 2-3 times in rapid succession. I even had the car towed to a reputable auto electric shop and they didn't charge me a dime because they couldn't figure out what was happening.
I think Daniel if you use the 1g to 3g tech article you will not regret it. In addition to the increased amperage, you can do away with the alternator harness, external voltage regulator, and associated old wiring. If an idiot like me can do it, anyone can.
