I just installed a new Powermaster 90 amp alternator on my car along with a new VR part # BWD R296. It seems that with these two new parts there were multiple directions on installation. One way I would not get a reading from the alt showing a charge and nothing on ammeter in car. Another hooked up way, the ammeter would jump from the middle of ammeter to pegged on C with interior lights flickering etc. Hooked up the other way my ammeter would still flicker but when revving it up, the needle would straight out peg on C. I'm clueless on whats going on or even what to check. But previously before the new stuff, my ammeter would sometime hold right above the middle bar and then would just peg out, then would get normal again.

the stock ammeter is only made for 40/60 amps so sending 90 amps of charge thru will melt it and peg it out. Bypass the ammeter and install a volt meter.

With new compatible parts there is only one correct way to install them. Details?

Just because the alternator is rated at 90 amps doesn't mean it's putting out that much all the time.

I am working on the very same problem on a 73 charger that I also installed a Powermaster alt and new voltage regulator (mopar) . This is the dual field alt and regulator with the triangular plug. I have the same exact situation with my setup. I bypassed the ammeter gauge and ran a 6 gauge wire from the alt directly to batt pos. and just hooked up a volt gauge inside. I confirmed the readings with a digital volt meter at the pos batt term as well as the alt. output stud and get the fluctuation . I also notice that when it fluctuates, the alt. makes a sound also (maybe corresponding to the higher charging rate).

I just tried a 2nd new volt regulator and same thing. I have a few other things to look at, but i am running out of ideas also. I don't think it is the alternator .

I believe it IS the alt. Electronic regs either work fine or go open (which'd show a constant discharge) or full field & allow the alt to max charge (& when they act up (not often) they stay that way). I'd visual on the brushes/brush holders for anything loose & something/somewhere is intermittently grounding (full fielding) the field circuit. it is possible that with the part time open it shows a discharge then when the open makes contact again the ammeter shows a high charge or a maxed out charge (pegged) as it is trying to catch back up (depends on how long it is open & the loads at the time. Dig in & holler with any news

The direction on the alternator states that if you previously have a one field system, use either field terminal and ground the other. On Powermaster website ( part # 7018 ) it specifically says to ground THIS terminal. At this time it is not grounded. The only way that I was able to get the alt to put out was to run a switched power to that terminal. It did not work when I grounded that terminal. I had to get power there. Right or wrong, IDK.

Grounding one field terminal is only if you're using the pre-'70 regulator, the regulator P/N in your OP is the '70 and later and it's wired like the diagram below.

Would the ballast resistor have anything to do with this? Any way, what is the correct ohm needed for the 68' Barracuda?

John I'm gonna check my wiring compared to this diagram. Thanks

Its actually a very basic system but you have to know if the alt you now have is like the Mopar alt or not. The Mopar alt is just two field brushes and on the electronic reg type in the wiring John posted just uses two insulated brushes so it needs 12 volts in one brush and through the field winding (rotor) and out the other brush to find a ground in the reg. The older type with mech reg had the 12 volts to the alt controlled by the mech reg and then into the alt field through a brush and then the other brush grounds it. Basically the old mech type just controls the field voltage before it gets to the alt field brush and the newer type with the electronic reg controls the field after the current leaves the alt as the electronic reg controls the field ground. I hope that helps some. Can you post a pic of how you have it hooked up ? Ron

i had a problem similar in that it was an intermittent discharge, or full field. i checked everything wiring wise, and it was wired correctly. it was finally traced to a cracked brush holder that was cracked at the hold down screw hole. replaced the holder and it's still going today ! was really frustrating to find, but the fix was easy. let us know the outcome please.

FWIW...the factory ammeter in my cuda shorted out and burnt the dash and engine wiring harness. When it happened, the ammeter was bouncing back and forth like you described. This was with a factory 60 amp alternator.
I'd get rid of it and install a voltmeter.

THIS...........Did it years ago and also ran separate alt wires bypassing the stock bulkhead and goes to 14.5-14.7 the second it starts......

Give Powermaster a call. I've worked with them before and got the best customer service anywhere. The first thing I noticed is they didn't start by telling me it was my fault. They worked with me and even contacted me later to check on my progress. I hope it works the same for you.

Also remember as someone stated that the alt will only put out what it needs to maintain the target voltage of the reg setting. You could put a 200 amp alt on the car and as long as its regulated right by the regulator it will only put out the needed current to maintain the voltage setting. So if you still have a mostly the stock setup but added a few things like electronic ign and fuel pump and fan that even with a battery close to dead the alt will put out just what it needs to hit the 14.5 or there about target voltage. Even with a 200 amps the alt may only need to put out 70 or 80 amps to maintain the target volts and supply the electrical load. Its always good to upgrade the wireing and bypass the ammeter and bulkhead connector on our older cars when larger output alts are installed but if you have not added much electrical load its not like it will fry your wire harness right away. I am guessing you are sure the alt you got does not have an internal regulator ? Ron

I need to draw up a detailed diagram for ya'll to see what may be the issue. Thx.

I'm running a 60 amp round back Power Master. We bench tested it and it showed putting out 14.75 volts. I converted the amp meter to a voltmeter.

DO IT before it melts. They are nothing but a fire waiting to happen.

I have the same alt. & land up changing the v.r several times before I found one that worked.I have new wiring and amp. gauge.
I get about 14.7 on the volt gauge autoflow aftermarket.The amp.gauge will peg if the battery is low or if I haven't driven the car in awhile but it slowly comes down a little past the center.I'm not worried as long as the volts are ok.I had the car checked and they didn't find anything wrong.
Btw even though it's 90amp. alt.it will only produce the amps. it needs.

Although it will only output the amps it needs, the ammeter, being resistive will drive the alternator to high output. The ammeters in these cars are old. the resistance will cause a meltdown(at best) or a fire. The symptoms described are a precursor to the latter...