Over the winter I switched to a 150amp PowerMaster Alternator (8142), when switching over I ran a dedicated line to master cut off switch with a solenoid so I when I cut power it killed everything. I used an 8 ga wire from the alternator to the firewall and a 3ga wire from the firewall to the master cut off. I also wired in a 100 amp fuse in the back before the solenoid and a 120amp circuit breaker by the alternator, so to have protection from both ends since I have power coming and going. Starting a few weeks ago I would randomly have the circuit breaker trip, its done it maybe three times.

I was out with the car Saturday night and noticed while in the staging lanes my volt meter had backed off to 12 volts, usually shows over 13 when idling with the fan in low. The more I rev'd the more the volt meter fell back, I turned my fan on high which usually makes the meter run to 14 volts and it fell below 12 volts, so I figured the alternator was not charging. I load it up, bring it home and the next day I start it and for the for the first few minutes it runs up to 14 volts like normal, but then stops and the voltage moves back down to 12. I checked voltage on both sides of the circuit breaker and it shows the same, so I assume it is getting 12v from the battery.

I am leaning toward replacing the voltage regulator but am curious if the random circuit breaker trips may be a grounding issue or possibly a wire size issue between the firewall and alternator. The on-line calculator showed the 8ga would be sufficient for the length of run (4ft). Would either issue (wire or ground) kill the voltage regulator?

Are there other things I could check or test?

Any help is appreciated.

When you checked the voltage on both sides of the circuit breaker where did you attach the ground? I would make certain that the alternator is grounded. I would do a voltage drop test between ground and the alternator case.

https://safe.menlosecurity.com/doc/...17d5e9fcf91290822967a812550aa32085f98fd3

Joe

I was told by a older Powermaster tech to use a #4 gauge wire from their 100 amp single wire alternator to the cut off switch in the trunk on my S/P bracket car with two 850 CCA marine deep cycle batteries mounted in the trunk on my 1970 Cuda. That was several years ago
I call them again earlier this year and talk to a different younger tech rep on using one of their 150 amp single wire alternator for a similar car(1969 Roadrunner) with two 1000 CCA deep cycle marine batteries, he suggested using either #10, #8 and or #6 copper wire, I used the #8 and grounded the alternator on its grounding lug with a short piece of #4 copper to a threaded hole in the cylinder head near the alternator I haven't ran that car yet so I'm not sure if I chose the correct wire size or not
I'll check it for heat after a run at the batteries at the races
I use a 100 amp stock alternator in my old pump gas Duster, I bypassed the amp meter with a piece of #10 gauge wire and ran a #10 wire from the alternator to the battery cable on the starter solenoid on the firewall and added a Voltmeter that worked only with the key on in the run position so it wouldn't drain the battery with the battery cut off switch left on