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Old 12-29-2004, 01:44 PM
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66 Mustang charging problems. Pulling my hair out...

Hi everyone. This is my first post here, but I've been reading the boards for a while now, benefiting from everyones tips and solutions.

I have a crazy charging problem on my 66 Mustang that I just can not fix, and I'm hoping that someone here might help me see this in a new light.

Last October my wife bought me a 66 Mustang as a Christmas present. (Although I had to pay for it, LOL)

A friend of mine who's an amateur mechanic helped me pull the 289 in it and we replaced all the seals, installed a new carburetor and a nice HEI distributor from Summit.

The 3-wire alternator, and the external regulator were both supposed to be new, but I do not know whether or not the car was actually charging properly when it was bought by my wife. As far as I know though, the alternator is just a replacement alternator, nothing special, probably either a 55 or 65amp like the original.

The car starts and runs beautifully, but it doesn't appear to be charging. I only read about ~12.4v to ~12.6v while the car is running. I took the alternator to autozone and had them test it on the bench and it ran up to 16+ volts. I put the alternator back in the car and I replaced the regulator with 2 different electrical regulators (1 new and 1 from a working 68 mustang) with no change in the situation. Still reading ~12.4v. It now has an electro-mechanical type I picked up from O'Reilly Autoparts.

I checked the resistance on all the wires running between the alternator, regulator and starter solenoid and they all checkout.

Over at the boards at fomoco.com someone suggested that I jumper the field and armature wires to bypass the regulator to verify that the alternator is actually working while in the car. I did this and the voltage at the battery ran up to almost 17v while it was running.

This tells me the regulator isn't working, but I've tried a total of 4 different regulators with no effect. I thought maybe this could still be wiring issue, pulled all the wiring from between the alternator and regulator and replaced it. Again, the resistance an all the wires check out.

I've checked the grounds all over the car. The engine is properly grounded, the firewall is grounded, the regulator is grounded, the dash is grounded. Everywhere I checked it, it read ~12v.

Last night I pulled the cap off of the electro-mechanical regulator and watched it closely as my wife turned the car on. It never moves to engage. But jumpering the two wires produces current.

I'm pulling my hair out over this one. Am I missing something? I'm so very tempted to just give up and buy a 1-wire alternator, but I don't want to just put a bandaid on the problem, I'd like to actually fix it. Not only that, but MAD's electrical tech about 1-wire vs 3-wire has me wondering if doing it is best for my car.

Please, I'm drowning here.. can anyone help?

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Old 12-29-2004, 03:21 PM
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mustang

I had a similar problem with a 74 Mustang 2. We changed everything. It ended up being a bad connection from the voltage regulator slip on plug to the regulator connector pins. I hacked it out of the car and put in a new one. Car ran fine.
I had the same problem with the wipers in my 79 vette. The wires all read good. It just wouldn't get power from the female plug to the pins. I cut the plug out and soldered the wires to the pins and the wipers work fine.
I hope this helps.

Last edited by bracketeer; 12-29-2004 at 03:29 PM.
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Old 12-29-2004, 03:46 PM
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Re: mustang

Quote:
Originally posted by bracketeer
I had a similar problem with a 74 Mustang 2. We changed everything. It ended up being a bad connection from the voltage regulator slip on plug to the regulator connector pins. I hacked it out of the car and put in a new one. Car ran fine.
Thanks for the reply. My plug also had corroded connectors, so I cut it off and re-crimped new spade connectors on each wire. I also did this up where the alternator harness connects. It was corroded and someone had done a redneck repair job. I cut it out and rewired that section completely.

Oh, I also forgot to mention that I've used two different batteries amidst my trouble shooting here. One from the 68 that's known to be a good battery. Hell, I've never seen batteries that will hold a charge this well after so many cranks and no charge. =)
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Old 12-30-2004, 02:27 AM
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Maybe there is something in this article that may shed some light,http://www.madelectrical.com/electri...esensing.shtml
or this, http://www.madelectrical.com/electri...witworks.shtml
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Old 12-30-2004, 08:08 AM
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first, the alt/reg may not kick in to charge till 1500+ rpm,

a points car was designed for 12V max at idle knocked down to 9V at the coil so the points don't burn up.

second, you need a volt meter to confirm the guage is reading correctly. alligator clip the V meter in place of the volt meter, run the motor up to 2k rpm.

compare that reading with a reading at the alt and batt at 2k
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