Hello,

Ford f100 1972
360 V8
Pertronix ignition
MSD 6a system
V belt

I installed a PowerMaster 47759 200amp 3G Alternator purchased from Summit Racing today and everything seemed to work without a hitch. First start up it was getting 14.5v or so. No squeal (patted myself on the back for that). I put it in drive with the parking brake on and let it run 15 minutes with the AC turned up all the way, stereo turned up loud (big stereo - 8 speakers, 2 subs, 2 amps - hence the new alternator) , and the brights turned on - didn't drop below 13.8v or so running at only 600rpm and mostly stayed over 14v. Honestly I was pretty impressed.

I turned it off, checked the tension on the belt... all good.

Fired the engine back up and my volt meter jumped right up to 18v. I didn't change anything. And no matter what I try now it's in that 18v range when it's running.

I tried the green and red wire at both the original green/ red location at the voltage regulator. And on a run/ start wire coming off my ignition pigtail. Have a resistor run inline on the wire per PowerMaster's instructions and have tried it both with and without.

I tried running the yellow wire both to the B+ terminal on the alternator and to the battery side of my solenoid.

I did not ground the alternator using the ground point on the back. The space between the motor and the alternator is just too small. Do I NEED to ground the alternator? My understanding is that it gets its ground just fine through the lower bolt right into the block. Can I ground it somewhere else - where? Do I need to reclock the alternator to access that specific recommended ground point (is there a way to di that without taking off the pulley again? A buddy had to help me swap out the serpentine for the v belt and I hate to bug him again).


Have 4 AWG with 175amp mega fuse running from B+ to battery side of solenoid.

I'm wondering if maybe the MSD system or my Pertronix may change the wiring somehow?

Or one thing that's strange about my original voltage regulator is there is no wire at the "i" terminal. I have two yellow wires on my "a" terminal and the green/red wire is actually on my "s" terminal. My "f" terminal is still orange. Old alternator worked fine except in stop and go traffic so wiring was fine for the 1G alternator.

Is the alternator just faulty?

What else can I try? Any tests I can perform?

Thanks.

 

The yellow wire is the important one for voltage regulation. They call it the "sense" wire in the instructions below. If the yellow wire has 12v on it with the engine off, I would say your alternator is bad. I would jump the yellow wire like they have it in the instructions below. Bring the green wire over and then take the old regulator out.

https://static.summitracing.com/glob...%201_25_11.pdf

 

Spoke to powermaster today. They wanted me to add a ground wire to the alternator. So I did. Grounded with 4 AWG between the back of the alternator and the battery negative. Checked the ground with my multimeter and registers 2 ohms all over the case of the alternator. Still no joy.

Put the yellow sense wire back on the B+ terminal of the alternator. What's interesting here is that I still have the same problem. But when I start up the truck it PAUSES for a sec at 14v and 16v before going straight to 18v. If I have it on the battery side of the solenoid it goes straight to 18v.

Checked that yellow wire when the engine wasn't running and showing battery voltage. 12.5 volts or so.

Think tomorrow I'm going to be asking Powermaster for an RMA number or whatever they need. Unless anyone has any other ideas.

Thanks

I know - beating a dead horse, but I'm used to things being MY fault - not faulty. Haha.