68 with 60amp Alternator - Not Charging

[strang3majik]

Hey everyone,

I've been working on my dad's 68 charger trying to figure out why it's not charging...this is an out of nowhere scenario.

It is a 1968 Charger with the 1970? charging system...60amp alternator.

Battery, voltage regulator, alternator, and ignition switch are all new. Grounds are good.

I tried running the B+ directly to the battery from the alternator with no effect...however, if I disconnect the blue field wire and jump a wire direct from the battery, it will charge. I assumed this meant the ignition switch was bad, but, that did not cure it. With the car running, I am getting around 9v at the blue wire.

I have everything hooked up exactly as seen here on the right. I am open to any suggestions...I've done wiring and engine swaps on far more complicated cars and this has me stumped. Haha.

 

[Shorthorse]

Make sure the regulator is well grounded as in the drawing on the right. The outer case is usually covered with a thick coat of paint and even bolted to the firewall will not ground properly.

 

[strang3majik]

Make sure the regulator is well grounded as in the drawing on the right. The outer case is usually covered with a thick coat of paint and even bolted to the firewall will not ground properly.

Okay, I will definitely check that. I did scratch the paint on the regulator and check continuity to the chassis but perhaps its not a very solid ground.

 

[RT K_line]

Is the Ballist resistor 2 prong or 4 prong? 70 and newer should b 4 prong.

 

[texas69bee]

And you are using a 2 field alternator?

 

[strang3majik]

Is the Ballist resistor 2 prong or 4 prong? 70 and newer should b 4 prong.

The ballast resistor is a 2 prong. It has worked for probably 10 years as is and the ballast resistor was replaced recently due to a no start.

It has two wires to each connector per side going to/from the resistor though.

What's the difference between 2 and 4 prong ballasts?

And you are using a 2 field alternator?

Yes, this is a two field alternator. 60 amp...1970s style.

 

[Mopars & Missiles]

Is the Ballist resistor 2 prong or 4 prong? 70 and newer should b 4 prong.

The ballast resistor is part of the "ignition system", it has nothing to do with the "charging system". Plus, his car is a '68.

 

[Mopars & Missiles]

Yes, this is a two field alternator. 60 amp...1970s style.

I started to post much earlier about the "two wire field" alternator you are using, but then deleted it because I saw you stated that it was wired "exactly like the diagram on the right". So, are you SURE it is wired exactly like that?

With a "two wire field" alternator, it must have the two wires attached to the field terminals from the '70's style regulator/wiring harness, OR one wire attached from the '69 and earlier style regulator/wiring harness WITH THE SECOND TERMINAL GROUNDED! Just double checking.

 

[RT K_line]

The 4 prong resistor has different resistance if I remember correctly. top and bottom were different ohms across the units. It's been a while since I had my 70 GTX but I recall having a problem if the U shaped opening on the side was facing the wrong way. But in your case it worked as it was, then you need to check where the blue wire connects to the resistor to see voltage. You said if you put B+ voltage to the blue wire it charges correct? I'll try to find a different diagram and see what the difference is. Someone chime in if I'm wrong please.

 

[Mopars & Missiles]

The 4 prong resistor has different resistance if I remember correctly. top and bottom were different ohms across the units. It's been a while since I had my 70 GTX but I recall having a problem if the U shaped opening on the side was facing the wrong way. But in your case it worked as it was, then you need to check where the blue wire connects to the resistor to see voltage. You said if you put B+ voltage to the blue wire it charges correct? I'll try to find a different diagram and see what the difference is. Someone chime in if I'm wrong please.

OK, I see your point. If someone changed the factory wiring at the ballast, he could be getting the reference voltage off of the wrong spot. Normally with the correct factory wiring this isn't an issue because the wire to the regulator coming from the ballast connection is the battery reference voltage and this junction point is just a "common splice point" in the wiring. The ballast does not affect this battery voltage reference, BUT if his wiring is all hacked up and someone mistakenly spliced the reference voltage wire for the regulator into the OTHER side of the ballast, then YES, the regulator would be getting a LOWER reference voltage. BUT, if this were the case, it would cause the alternator to OVERCHARGE whereas his issue is NO charge at all. Hope that all makes some sense.

Again, if wired correctly the ballast is NOT part of the charging system, merely a wiring tie point.

 

[strang3majik]

I started to post much earlier about the "two wire field" alternator you are using, but then deleted it because I saw you stated that it was wired "exactly like the diagram on the right". So, are you SURE it is wired exactly like that?

With a "two wire field" alternator, it must have the two wires attached to the field terminals from the '70's style regulator/wiring harness, OR one wire attached from the '69 and earlier style regulator/wiring harness WITH THE SECOND TERMINAL GROUNDED! Just double checking.

Yes, it has the newer regulator and the newer alternator.

I traced the wires from the field connections and the green goes direct to the voltage regulator and the blue goes back to the firewall and splits with one going to the voltage regulator and the other going to the ballast resistor.

I do have voltage on both field wires as well with the car running, though neither is a full 12v...they were both around 9v

I haven't traced the B+ wire, but its has full battery voltage when the car is running, so I am assuming that is hooked up correctly.

Also, battery is grounded to the radiator support and the engine block, and there is one going from the engine block to the firewall. I also ran a ground from the alternator body direct to the chassis with no change either.




And yes...if I put B+ to the blue terminal, it will charge, however the car will not turn off with the key. Lol. Not sure if that is normal, but with the key off, I had to cut that jumper wire for the car to turn off. By running that wire, I am technically bypassing the ignition, though, so, perhaps that is why.

 

[Mopars & Missiles]

Sounds like you are doing it correctly. In theory, the blue wire is the +12 volt battery reference that the regulator uses to determine if the alternator needs to charge or not. The regulator also has to have a ground reference which is of course through the metal case to chassis ground (the firewall). The regulator monitors these two reference voltages and controls the alternator output via increasing/decreasing the field coil current depending on whether the monitored voltage is too high, or too low.

On the '69/earlier models the alternators were a single terminal field coil that was internally grounded. The regulators switched the POSITIVE side of the field coil. This causes a lot of arcing when the contacts open and close, and causes more wear to the contacts and premature failure of the regulator.

On the '70 and up alternators they used a two terminal ISOLATED field coil and a two wire regulator. This new design still used the same two reference voltages as before, but now control was accomplished by switching the GROUND side of the field coil instead of the hot or POSITIVE side. This resulted in much better reliability and longer life of the regulator since switching the ground side greatly reduces the arcing across the switch contacts (it was actually a transistor switch now instead of the previous mechanical contact type).

I know, long winded and you probably already know all this but maybe someone else will benefit that didn't quite understand how the two systems work.

 

[PurpleBeeper]

I suggest you take a second look at your wiring. I "think" you should have 12V at both of those field wires, which makes sense based on what you say (works if battery voltage put to that field terminal). My "guess" is that this blue wire is getting voltage AFTER the ballast resistor instead of BEFORE (voltage being stepped down as power goes through the ballast resistor). And on a side note, my '70 came originally with a 2-post ballast resistor, not a 4-post.

 

[texas69bee]

Maybe this will help. The 5 pin ECU uses the 4 pin ballast and the 4 pin uses the 2 pin ballast. Like stated before it's not part of the charging system but may help you in wire routing.

 

[RT K_line]

Thanks for that diagram texas69bee, now I see why I had the 4 prong resistor since I upgraded to electric ignition. I thought the extra resistor was related to the charging system. My mistake I plead old age, It was 25 years ago at least. LOL

 

[oldbee]

Thanks too all you guys---it's been at least 30yrs since I had to think this stuff through & brought back old memories. 1-wire alternators on diesel trucks and all the old memories are way back in the databank!!!!

 

[strang3majik]

Thank you for the assistance everyone. I will be checking it out again tonight.

Also, Mopars & Missiles, thank you for the explanation...I actually was not entirely sure how the system worked and that cleared it up quite well! I will double check the chassis ground to the regulator again, just to make sure.

I'll check the ballast resistor as well to see if the blue wire is on the wrong side of it. Not sure how that would have happened, but, anything is possible. I can tell you I am not getting 12v at either of the field wires, though.

Thank you as well, Texas69bee for the diagram of the ignition system. Not sure how he has it hooked up, but I know my father did that conversion in the 80s. Haha. Not sure if he has the 4 or 5 pin, but he does have the Chrome box.

I will keep everyone posted! If anyone has any other ideas, I am open to hear them. Lol!

 

[strang3majik]

Okay. . . I have an update.

Voltage regulator is grounded and the blue field wire is on the correct side of the ballast resistor. . . However. . .

At the high side of the ballast resistor and both field wires, I am only getting 11.5v. At the battery I am getting 12.3v.

If I rev the car up I get 12.5v. So it is charging but not enough.

And somehow between the battery and the ballast resistor I am dropping a whole 1v of electric.

I have a feeling that is the issue. . . The 11.4v isn't enough to full activate the field.

But what would cause a voltage drop between the battery and the ballast resistor?

 

[Mopars & Missiles]

Okay. . . I have an update.

Voltage regulator is grounded and the blue field wire is on the correct side of the ballast resistor. . . However. . .

At the high side of the ballast resistor and both field wires, I am only getting 11.5v. At the battery I am getting 12.3v.

If I rev the car up I get 12.5v. So it is charging but not enough.

And somehow between the battery and the ballast resistor I am dropping a whole 1v of electric.

I have a feeling that is the issue. . . The 11.4v isn't enough to full activate the field.

But what would cause a voltage drop between the battery and the ballast resistor?

Wiring connections. The path goes through the bulkhead connector twice......there's plenty of potential problems right there. It also goes through your ignition switch, another voltage drop area possibly, then there is also the ammeter which could be causing a voltage drop as well. This is the most dangerous one due to possible dash fire issues.

 

[Nacho-RT74]

Bad diode at alt?