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My alternator for my 66 LTD, 352, non AC car has failed. I have had the ALT red light start to come on, and the battery is getting weak, voltage wise. I did a test of the voltage regulator, jumping the A and F terminals, and the voltage didn't go beyond the 13 volt range, so I surmised my regulator was fine and the alternator may have issues. I also had an older voltage regulator that I know was working, and did the same test, and had the same results.

I pulled the alternator and took it to my local parts store, where they ran a bench test. It failed half of the tests. I did not take a picture of the results, which would have been a smarter thing to do. But, since it failed at least half of the tests, I figured that would be a good sign the alternator was probably bad. It is an older Autolite alternator, it could possibly be original to the car.

I did replace the voltage regulator with one from AutoKrafters last month, the spec on that was for a car without A/C, 38/42 amps. AutoKrafters also sells an version for a car with AC, 45/55 amps.

So, if I replace the alternator, I am guessing I should replace it with one rated 38 Amps, to match what amps the voltage regulator I have purchased can handle. I run no other non factory accessories on the car, so there is no aftermarket parts to power. I would like to get a higher capacity 55 AMP alternator, but will I then have to change out my voltage regulator from the 38 Amp version to a 55 Amp version? Never really thought about this before, so before I buy another alternator, should I be matching it with the same capacity voltage regulator, or are the voltage regulators pretty adaptable up to a certain amperage and I would not be hurting anything?
 

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Thanks for that quick reply extech. But, I am still not sure of the answer from what you wrote. Maybe I need to clarify.

If I put a 55 amp alternator in my car, which was originally spec for a 38 amp alternator, do I have to swap in a higher rated voltage regulator that can handle more amps? Maybe the AutoKrafters catalog is wrong, but they are selling 2 different voltage regulators for my car that seem to be pointed to the output of the alternator installed on the car, either 38 amps, if you dont have AC or 55 amps, if you have AC
 

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From doing more research, it seems that the cars with AC and other power accessories are the ones that got a 55 Amp alternator. I doubt the internal wiring harness is different regardless of if the car had AC installed or not. So, I am somewhat confident that a 55 Amp alternator will not damage my system. Will it help since I don't have any accessories other than the stock factory ones, and no AC or power windows or seats, I doubt it, but won't hurt.

I am going to replace the mechanical Voltage regulator with a electronic one, and try to just pop the top cover off it and put the repro one from the mechanical one on it. That way, I wont have the worry about if the voltage regulator is going to get fried if I use a 55 Amp alternator vs a 38 Amp alternator that the car has been using the past 54 years.

And, attached, the test on my alternator from the parts store, it certainly looks like it isn't putting out the voltage that it is supposed to.
IMG_4886.JPG
 

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the test shows you have a bad diode. the larger current alternator wont put out more current than needed. that current is only used by the battery
 

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My alternator for my 66 LTD, 352, non AC car has failed. I have had the ALT red light start to come on, and the battery is getting weak, voltage wise. I did a test of the voltage regulator, jumping the A and F terminals, and the voltage didn't go beyond the 13 volt range, so I surmised my regulator was fine and the alternator may have issues. I also had an older voltage regulator that I know was working, and did the same test, and had the same results.

I pulled the alternator and took it to my local parts store, where they ran a bench test. It failed half of the tests. I did not take a picture of the results, which would have been a smarter thing to do. But, since it failed at least half of the tests, I figured that would be a good sign the alternator was probably bad. It is an older Autolite alternator, it could possibly be original to the car.

I did replace the voltage regulator with one from AutoKrafters last month, the spec on that was for a car without A/C, 38/42 amps. AutoKrafters also sells an version for a car with AC, 45/55 amps.

So, if I replace the alternator, I am guessing I should replace it with one rated 38 Amps, to match what amps the voltage regulator I have purchased can handle. I run no other non factory accessories on the car, so there is no aftermarket parts to power. I would like to get a higher capacity 55 AMP alternator, but will I then have to change out my voltage regulator from the 38 Amp version to a 55 Amp version? Never really thought about this before, so before I buy another alternator, should I be matching it with the same capacity voltage regulator, or are the voltage regulators pretty adaptable up to a certain amperage and I would not be hurting anything?
Hello jdstefan66,

The thing with the original style points regulator is that it's a two stage oscillating relay with a high charge and low charge setting. In fact there is a current limiting resistor effectively in series with the field winding for low charge setting. So what you are doing is effectively matching the low charge setting resistor with the resistance and inductance in the field winding which of course is different between different capacity alternators.

Now that's with the old point oscillating mechanical regulators. I would strongly suggest you switch to the newer electronic style which just plugs right in. The reason why the old mechanical oscillating regulator did have two charging positions (high and low) is there is a limit to how fast the mechanical points could oscillate withcidentally is directly related to just how well it can regulate vehicle voltage. On the electronic version there is no high and low settings, it's just on and off. However, the electronic voltage regulator can switch much much faster with less electrical noise (has flyback diode on field circuit) and can control any 1G Ford alternator you put in the car.

A note on your old alternator, given the state of substandard (read as complete crap) rebuilds and even brand new alternators, I would also strongly encourage you to rebuild, if possible, your old one. I've bought a few and rebuilt new alternators and they all either had problems from the get go or developed them shortly. I could write a short dissertation on that subject alone.

One last point on the electronic voltage regulator to keep in mind. When you switch your 3rd gen Ford into the "Accessory" position, you'll notice the "ALT" light on. With the old mechanical point gap regulator under these conditions, the "ALT" lamp along with a resistor (wrapped in the wiring under the dash) is in series with the field winding in the alternator and there's little current flowing so you do not 1.) overheat the field winding and 2.) drain the battery quickly.

The problem with the new electronic regulator is when you put your car into "Accessory" position to say listen to the radio, the "ALT" lamp still illuminates but the newer regulators allow full field current which of course will overheat the field winding from not spinning and also drain the battery a whole lot faster. Now there are of course wiring tricks to alleviate this, but it's something to keep in mind.

Hopefully this helps.

Cheers
 

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Thank you DesertXL for your well thought out reply. You helped me understand the way that it works.

I am def going to replace the mechanical VR that I bought, even with that pretty Autolite cover, haha. I will get a electronic one and be done with the worry. And, I will see if I can transfer the Autolite top from the old mechanical one to the new one, since the top is pretty much for pure decoration at that point and I do like the stock look.

I will go with the rebuilt 55 Amp alternator from NAPA. I would like to heed your advice, but time constraints will preclude me from doing a rebuild of it, shame because the outer case is the original Autolite shell, on second thought, maybe I will keep the core, since NAPA is only charging $5.50 extra if you dont return the core.

I am now confident I am not going to fry any of my stock wires with the 55 Amp alt and a electronic VR. And, I will heed your advice and not play the radio in the ACC mode. I hated seeing the Red Alt light glow when I was parked, engine off and in the ACC position and playing the AM radio. I love AM radio, esp when you have a good oldies station to play, or classic rock, a rarity on AM these days. So, I just got into the habit of bringing my little transistor pocket radio to play in the car when I was parked eating, etc. Now I know that will be even more prudent advice once I switch to the electronic VR with the heavier battery drain you mentioned.

Thanks extech also for chiming in, appreciate the education. I obsess on these seemingly simple decisions, well, simply because I dont want to damage the car. I can proceed with comfort now.
 
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