Possible alternator and or voltage regulator issues?

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71DodgeDemon340

71DodgeDemon340

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Hey everyone. Ok so the 71 demon has been done for a couple years now and yesterday i started her up and immediately noticed a problem. First ill tell you my setup 340 with electronic ignition upgrade mopar voltage regulator and distributor and coil. Cant remember the size of the alt but its not a high output alternator but still using the ammeter guage in car and have replaced the fuse able link wire to a fuse type fuse able link. Ok so when i started her up immediately the ammeter guage went to +40 or all the way to the right and my interior lights were really bright well then it poped the 30 amp fuse in the fuse type fuse able link so i shut her off replaced the fuse and then fired her back up and it didnt pop it again but the ammeter guage was fluctuating between 0 and +40 so i shut her off and havent messed with it yet die to being sick but i want to know where is a good place to start looking or checking to track the problem down any help would be great thanks
 
Start with grounds on the motor and regulator, and then take a look at the bulkhead connector. (A good solid jiggle on this may tell you something)
Also chk the connections at the alternator.

It may just be the regulator like you mentioned, but this other stuff can do that too.

You also might want to do the MAD electrical bypass when you get a chance.
That is here http://www.madelectrical.com/electricaltech/amp-gauges.shtml
 
1.....What is this 30A fuse? If you are talking about a fuse replacing the original fuse link, that is not nearly large enough

2.....Has the car been sitting awhile? Is the battery down? If so, the very first thing is to determine if there "actually is" a problem. Run the car and check battery voltage. It should not be above 15 at the absolute most. Normally, voltage, running, charging, should be (depending on battery charge and regulator / battery temperature) should be loosely 13--15 volts

Once the battery is warmed, and charged back up, things should be "tighter." In this case, you should expect not less than 13.5, and not more than 14.2

And to get even tighter, optimum is 13.8--14.2 volts

3...There is a couple of preliminary things you can do. Get a legitimate battery terminal brush if you don't have one, and remove and clean the battery terminals

Remove the regulator, scrape around the mounting bolts and the regulator flange, and remount, using star lock washers. The regulator MUST be grounded

Remove the alternator field wires and work them on/ off a couple times to scrub terminals clean and to "feel" for tightness. Do the same with the regulator connector.

Check your belt for tension and slippage!!!!
 
Had a similar issue with my 69 Barracuda. Pegged the voltage meter. Replaced the voltage regulator and she's been charging great since.
 
Thanks will check grounds at regulator and the output voltage but the car is kept inside and all the terminals on the battery are clean but i will double check them is there any way to check the regulator on the car thanks for the replies im starting to feel better so i might try and mess with it tonight.
 
Hey 67 finally got a chance today to do some trouble shooting. So i remembered the guy my dad works with had give us a motor brand auto repair manual for 66-72 ford chevy chrysler dodge etc vehicles. And looked under the testing the voltage regulator section for wiring with an isolated field alternator. Also said to check with engine running at 1250 rpm and to place the black lead of the volt meter to ground and to take the positive lead and check voltage at the voltage regulator side of the ballast resistor. Normal voltage spec at that point should be 13.8-14.4 volts and if there was a difference of more than .5 volts than specs at that test point to replace the voltage regulator. So i fired her up and within 5 seconds or so we were reading 18 volts. Just to double confirm the manual the regulator is bad correct? Also i have a factory style on it now with the chrysler insignia are those ok or are there any better options thanks so much for your help
 
71DodgeDemon340 said:
Hey 67 finally got a chance today to do some trouble shooting. So i remembered the guy my dad works with had give us a motor brand auto repair manual for 66-72 ford chevy chrysler dodge etc vehicles. And looked under the testing the voltage regulator section for wiring with an isolated field alternator. Also said to check with engine running at 1250 rpm and to place the black lead of the volt meter to ground and to take the positive lead and check voltage at the voltage regulator side of the ballast resistor. Normal voltage spec at that point should be 13.8-14.4 volts and if there was a difference of more than .5 volts than specs at that test point to replace the voltage regulator. So i fired her up and within 5 seconds or so we were reading 18 volts. Just to double confirm the manual the regulator is bad correct? Also i have a factory style on it now with the chrysler insignia are those ok or are there any better options thanks so much for your help
Click to expand...

I'm not sure what you did here so let's clarify.

There's several reasons that charging voltage could be high

1.....Voltage drop in the ground circuit. What this means is, the regulator is not truely grounded to the battery negative, see below.........

2.....Voltage drop in the ignition harness which is VERY common

3.....Regulator out of spec, IE trying to regulate but high. This is far more common on the older mechanical ones

4.....In rare cases, a battery going bad. Easily checked if you can just swap in a known good battery

==========================================

To check all of the above, and what you MIGHT have been checking with your meter

A......To check the ground circuit, get the battery charged, engine warm, and battery normalized. Run this check with all accessories off, and again with heater, lights, etc turned on.

With your meter on low DC volts, stab one probe into the regulator mount flange. Be sure to stab through any paint, chrome, rust. Stab the remaining probe into the top of the battery NEG post. What you hope to read is a VERY tiny voltage, the less the better, and zero would be perfect. More than .3V (three tenths of one volt) means you need to improve regulator ground

B......To check harness voltage drop, find the "high" side of the ballast IE the "key" side Turn the key to "run" but with engine OFF. Measure this voltage to the battery NEG, and subtract it from the battery voltage. As in B1, below, you are hoping for a result no more than .3V (three tenths of one volt)

B1.....A quicker, more direct way, is to find the "high" side, and leave your probe on that terminal. Move your ground probe to the batter POS terminal. As in the ground check, you now hope to read a very LOW voltage, the less the better. More than .3V means you need to improve the ignition harness circuit.

B2.....I'm not really sure but I THINK you checked the above in a third manner. With the engine RUNNING, if you measure the "high" (key) side of the ballast, then measure the battery, this voltage difference will be the same as in tests B and B1. In other words, if you measure, say, 14.2 at the ballast, THIS IS what the regulator is regulating TO and is "correct." But if the battery shows HIGHER, then this shows you do have voltage drop in that ignition harness / ground circuit.

Common problems in this harness are the bulkhead connector, ammeter and connections, and ignition switch connector or the switch itself.

PLEASE read this:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

WHY this voltage drop is important: The regulator gets power through the ground circuit and the ignition harness circuit. Let's say between the two of them, there is a 1.5 V drop. This 1.5V gets ADDED to the battery charging voltage because the regulator "senses" whatever voltage is at it's terminals.

This means if the regulator is actually "correct" at 13.8--14.2, this 1.5V drop gets added to say, 14V so the battery now sees 14 + 1.5, or 15.5V
 
The manual said that correct voltage at that test point should be between 13.8-14.4 if the reading i got was .5 v or more from spec that the regulator was bad. And we were getting 18 or so at that point
 
The regulator is PROBABLY bad but what that test does NOT show is whether the regulator is actually grounded. Before you replace it, I would remove, scrape, and reinstall the regulator. Use star lock washers. Do the ground test I posted earlier.

If it still reads high on your test, then bad regulator.
 
Ok we used a wire with alligator clips and clamped one clip on the bolt head which has a star washer and has dug into the regulator body when it was tightened up and the other end of the test lead to the negative terminal on the battery and got the same result
 
Cool thanks for confirming my results lol i just like to double check. Also is the mopar performance regulator good or should i get a different brand
 
Boy I don't know I've actually got one of those I've been meaning to try, got in a part car. There used to be a warning in the MP cataloge "race only." The definition of "voltage regulator" is that it regulates voltage. So I"m not sure whether that "warning" is crap or what. I've seen posts other guys running those on the street.
 
If the new regulator doesn't fix the over-voltage problem, check the resistance from the green field wire (unplugged from alternator) to ground, with the connector unplugged from Vreg. If you read low resistance to ground (<500 ohm) that means the green wire is shorted to ground, which will keep your alternator at full output, independent of whatever Vreg tries to do.

I would make one change to the diagram in post #11. Instead of putting the black voltmeter lead on a random "body ground", place it on the case of Vreg. That is the only ground Vreg knows, which is the point in post #13.
 
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