Alternator, voltage output question...

[72.RS/SS]

Ok, so I installed a March under drive serpentine setup. My voltage used to run 14+ volts(while driving) with the under drive pulleys it was around 11 volts(while driving). I swapped out the alternator pulley for one that was the same size(actually a little smaller) as my old one and I wired my alternator to be a 3 wire, yet I still only run about 12.5 volts(while driving). My water pump pulley is the same size as the old one and the crank pulley is only 1/4" smaller, so it shouldn't be under driving the alternator any more. Last night I had it out after dark and my gauge was showing about 11.5 with the headlights on.

When the car is running I have 12.4 at the battery and the alternator. Pretty much every where else is getting 11.9-12.1. I drove the car about 175 miles with it under driven and only putting out 11.4 at the alternator. Do you think I damaged it. It is a Powermaster, I don't know what amp. I looked a part number on it, but can't find one.

I wired the 3 wires up with the one blade looped back into the charge stud and the other is being fed from a switched source from the fuse panel and has a 3amp diode. I have a 4ga wire from the charge stud to the starter lug, cause my battery is in the trunk. It hasn't left me stranded yet and starts fine. I just figure it will preform better with more voltage.

Can anybody find a flaw in anything or is the alternator going/gone bad? I can get the alternator check at pretty much any parts store, right? When tested it should put out, what? 14+ volts. Thanks all.

[Jim Nilsen]

You obviously have a very good battery, that low of voltage is not enough and will put a strain on the battery life. You should have a minimum of 13 volts with the lights off and at least 12.5 at idle with them on and go to 14 volts above 1500 to 2000 rpm.

You didn't say what your voltage was at higher rpm, if you don't have more than the 11.5 at driving rpm's and it truly is only 11.5 while driving you will eventually have other problems start to creep up on you. Igniton systems don't like low voltage. The alternator is still more than likely fine.

I myself have never liked underdrive systems to gain only a couple of horsepower. If you are racing for money it is one thing if you are just posing it will always cost you in some form or another that isn't worth the gain. There are lots of other places to pick up that little bit of HP.

I would put the old pulley on and stop worrying. But that is just me, others may have a different opinion.

[72.RS/SS]

I have already put the original size pulley on. That is the problem. I figured it would go back to 14+ volts and it didn't. The voltage never went higher(at the gauge) then 12.5 volts while I was driving. I didn't get any more with the multi-meter when I revved it up.

I took my alternator off to take it to Advance to have it tested and stuff was rattling inside it. I shook it up and little pieces started falling out. Some mystery pieces fell out and a piece of wire and a white plastic cylinder thingy. Guess it's off to Summit shopping I go.

[6'9"Witha69]

What type of 3 wire alt did you run?

The 3rd one you looped back to the charge line is meant to be remote voltage sensing. Just taking it off the charge stud negates the benefit of downstream voltage sensing.

http://madelectrical.com/electricalt...esensing.shtml

[72.RS/SS]

What type of 3 wire alt did you run?

The 3rd one you looped back to the charge line is meant to be remote voltage sensing. Just taking it off the charge stud negates the benefit of downstream voltage sensing.

http://madelectrical.com/electricalt...esensing.shtml

I ordered a new 140amp Powermaster. I plan to wire that 3rd wire into the horn relay junction.

I pulled my old alternator apart to see what was rattling. One of the wires in the center coils was broke off and the one of the brushes( I guess that's what it is) in the back was broke off. But that brush may have come off when I took it apart. The coils on the outer ring didn't look like they were in the best shape. Hopefully this one alternator fixes that problem.

[H2Ogbodies]

R u running v-belts? If so, grab an alt. from an 88 Olds Firenza with a 4 cyl. from a parts store....then get a HELP section 4-wire CS type pigtail and swap to an internally reg. system and run this 90-amp alt. You won't have any problems. You need to swap pulleys too-this one has a serpentine style one on it. PM me if you need help-this is a swap I do routinely for v-belt driven SB's. It has 12 and 6 clocking and has a 5.25" diameter case so it drops right in place of your old alt.

[72.RS/SS]

R u running v-belts? If so, grab an alt. from an 88 Olds Firenza with a 4 cyl. from a parts store....then get a HELP section 4-wire CS type pigtail and swap to an internally reg. system and run this 90-amp alt. You won't have any problems. You need to swap pulleys too-this one has a serpentine style one on it. PM me if you need help-this is a swap I do routinely for v-belt driven SB's. It has 12 and 6 clocking and has a 5.25" diameter case so it drops right in place of your old alt.

I have a March serpentine conversion. I already ordered the Powermaster. Thanks for the info though.