voltage regulator

70 roadrunner with 70 amp alt. constant output voltage regulator 3690731. been having miss in motor which turned out to be connection at ballast resistor. While trying to track down problem measured voltage going to ballast and it was jumping between 16 volts and 18 volts when car is running. 11.5 when not. Question is, this means Regulator is bad?

Sounds like a bad regulator ground based on the higher than desired voltage and the erratic behavior.

I am running a pertronix III with the multi spark would that make voltage at coil diffrent? I just tested my friends Chevy with MSD and its reading 25 volts at + side of coil.

I have a 70 rr also, 95amp. alt. mine was running 15-15 1/2 volts put this voltage reg. on and now I'm at 13.8-14.2.don't waste your time with local parts store ones I couldn't find one that worked.This is the one I used.
Mopar Voltage Regulator ( P4529794 )3438150 from summit.

I would think running at 20 volts it would burn everthing up.

It will if it hasn't started already.I wouldn't drive the car until you get the voltage down.
Maybe others will chime in.

The 731 is as you noted the race reg. get a regular parts house electronic reg & see if your voltage comes back down to an acceptable level. I would not run it until you do

So confused put a stock regulator on with a good external ground same thing now hovering around 20 volts but every so often 13.5 will flash on meter. Just think something else is going on.

Yes definitely something else going on. possibilities are that the green wire from alt to reg is intermittently touching metal/grounding out & making it full field for a split second and related thing with the alt brushes/field circuit (them grounding out & full fielding it. got another alt you could toss in for a quick test? for the "green wire" possibility, a good visual along its length or pull the triangle connector from the flat reg & pull the green wire off of the alt & with a jumper connect alt to reg (side terminal) and jump 12V (blue ign1 circuit) to the reg top terminal. the recessed reg nubs are a slight pain to jump. EDIT I'm wondering if it might be the digital meter? if you have a 12V bulb such as a 1157 lit up nearby does it change brightness when the meter changes reading?

thanks for the info will try tomorrow. I think its time to walk away for now. Been working since 6am and I'm spent/frustrated.If anyone has ahigh output alt with a pertronix III conversion please take a reading with digital volt meter at + coil while running and let me know what your reading. Thanks for the help

try reading this
http://www.highimpactperformance.org/files/mopar001_1_.pdf

Robert hope your still out there. Couldn't leave it alone. Did the green wire bypass 14.2 volts. KOOl so hook everthing back up normal its all working 14.2 volts now I'm really confused. I then relize to easy checking stuff I jump ground DVM to the body. If I ground meter to engine I get 20 volts if I ground it to the body I get 14.2???? I have ground strap from motor to frame. Battery is in trunk grounded to frame. Any thoughts from anybody?

Voltage regulator is grounded to the body, alternator is grounded tot he engine. The problem you are seeing is the ground between the body and the engine is bad.

Run a quicky jumper from the alternator case and voltage regulator and see if everything is as it should be.

As I suspected, with the two voltage readings, a poor regulator ground. Just not at the firewall. I agree with Supercuda, run a temporary ground between the body and engine and see what you get. One lead of a pair of jumper cables works great for this.

Ran jumper wire from alt case to body no change. Used jumper cables from bumper bracket bolts to motor mount bolts and power steering pump DMV jumping all over the place. My ground cable runs from intake manifold bolt to sway bar bracket bolt on k member. Being manifold and heads are aluminum could this cause grounding problem?

Why are you reinventing the wheel.

Your ground choices are not good ones.

Run the jumper from the ALTERNATOR to the REGULATOR directly.

Anything else is just wasting time.

Okay will do thanks. will post outcome.

After your last post I am not so sure I'm right. Try two things. First with the engine running take a voltage reading between the alternator case and the body. This will check how good the ground is. Second with the engine running take a voltage reading between the output stud of the alternator and the battery post on the starter relay (I'm assuming that's where you terminated your remote battery lead). This will check for voltage drop on the positive side. Problem may be on the positive side and not the negative (ground) side.

Will do . What kind of readings am I looking for between Alt case and body?

Both cases are similar. If you have a good ground between the case and body you should read close to 0 volts. If you have anything else, what you are measuring is the voltage drop through a poor ground connection(s). If you have a good connection between the alternator output stud and the starter relay stud, you should again read close to 0 volts. If you have anything else, what you are measuring is the voltage drop through a poor connection(s) on the positive side. You have to keep in mind that the system voltage the regulator is using for a 'sense' voltage is coming from the stud on the starter relay through the ignition switch.

Okay ran jumper wire from alt case to regulator. Same thing shows 14.2 at + coil if meter is ground to body, shows 20 volts if grounded to motor. alt case to body shows 4 to 5 volts. alt output stud to starter relay stud shows 8 volts. Battery shows 14.2 charging all with car running.

8 volts? Holy crap, Batman. What I would recommend you do now is run a jumper between the alternator output stud and the starter relay and redo the readings. If the voltage difference from the alternator to the starter relay is now near 0 volts you have a poor connection in the wiring from the alternator to the starter relay. Biggest question at this point is do you have the stock ammeter? The stock charging circuit goes alternator to bulkhead terminal, bulkhead terminal to ammeter, ammeter to bulkhead terminal, bulkhead terminal to starter relay. If the jumper between the alternator and starter relay worked, then you have a poor connection somewhere in the above path. If you have eliminated the ammeter, then you will have to determine where a poor connection may exist based on how you modified your system. The other voltage between the alternator case and body should wait on what you find out with the above tests.

stock ammeter but solid wires to and from not threw the bulkhead connecter. Next wierd thing, I still have jumper wire from regulator to Alt case, when measuring voltage with the DVM red lead on + coil ground on jumper wire at Alt reads 20 if I move ground to jumper wire clipped on regulator it reads 14.2 how is this possible on same wire? 1 of the readings has to be wrong. If I have been running all this time with 20 volts to coil and electronics I got to believe it would have fried something by now.

Agreed, can you borrow another meter from someone for an hour, preferably an analog? or at least another digital. EDIT I suspect you are actually at 14.2 (high end but good) & for some reason the meter ain't stabilizing (poor connection/bad meter).

Thats my next move something is just not right. I hooked up again to my sons Nova with MSD ignition it again shows 25 volts on + side of coil. To many conflicting readings. I Thanks everyone for all the help. Holiday weekend everone else at track Maybe can borrow meter tomorrow.

I missed the comment you made about "...flash on meter...". After being misled by more than one digital VOM, I quit using them for general automotive use. Strictly analog for me.

The MSD doesn't work like other ignitions, I'd only be concerned with voltage readings at the battery.

Basic facts...The Pertronix III is a multi-spark ignition. That makes the hot wire between the module and the coil part of a resonant system and voltages you measure across the coil are meaningless.

The MSD6 is a capacitive discharge system and the capacitor hits the coil with tiny bursts of high voltage, somewhere around 450 volts, one hit for every spark. When you put a voltmeter on that it measures the "sorta" average voltage. Again, meaningless.

I have run the 732 "Race only" voltage regulator on the street since 1984. It's the same internally as the 731. There is nothing inherently wrong with either regulator. My charging voltage measured across the battery terminals is roughly 14.3 to 14.5 volts, just what a modern maintenance-free battery likes to see. Some have suggested it's race only because it does not bias charging voltage to the temperature. Could be, but it is meaningless as well because it just flat works. My batteries last, on the average, 7.5 years. One thing this regulator did is keep enough charging at idle that my headlights do not act as a visual tachometer any more.

Grounds are very important and need to be policed every once in a while. Also, the suggestion to ground directly to the alternator case or the battery negative post is right on.

Finally; when someone shows up with a "problem" the first thing to do is analyze if it really is a problem. Everyone jumping on their horses and riding off in all different directions does nobody any good. The stock answer to buy a new one doesn't help either, not until the real problem is identified. In some cases the best suggestion would be to get different friends, if the friends are terminally ignorant. (Especially Chevy Know-it-alls.)

Warmest Regards,
R.

Agreed I am begining to believe I real do not have a problem. I re-did all the grounds added extra ones and nothing changed.Like I stated earlier if I was really seeing 20 volts the system would have fried along time ago. I have also run this 732 regulator for 20 years with no problems. I think the 40 year old dash harness doesn't help either. The bullet connecters to ignition switch are old and brittle. I have hard wired several of them. I still would like to thank all who chimed in to help with this problem.

An eight volt drop? I don't care what kind of ignition you have, this doesn't sound right. Either there is a problem with the multimeter and there is no wiring problem or there is a legitimate wiring problem. May be some of both but to walk away with the conclusion that I haven't smoked anything yet so I must be OK.....

Not walking away from analizing problem. Just need to regroup and give it more thought. I know something isn't right. Looking at 40 year old wiring.