Charging issue for the electrical guru's

[YellowThumper]

I did not skimp on that.
IIRC it is 0/1 or 1/0. Well over normal battery dia. The ends are also soldered on. Not just crimped.

[Chryco Psycho]

 The regulator switches the ground to the field circuit of the alt , so if the voltage is too high out of the alt it turns off the field ground , when the voltage is too low it grounds the field , so the alt is truely controlled only by the regulator , the exception to this is if one of the diodes fail then you can have under charging or overcharging but it would not be intermittent . The reg has to be properly grounded as it switches ground for the field circuit .
Resistance through the bulkhead will always cause problems & most have heated up from corrosion & melted at some point , , newer cars have eliminated the bulkhead plug & just run 1 harness inside & out .
If everything i good there  it should be a bad reg , if the rubber seal in the back is not secure moisture can get in behind & short the circuit board , I generally had to install a new reg once / year in my 89 Cummins truck as the moisture would get past the seal & short it out .
16v means the field circuit is constantly grounded & the alt is putting out max power , or a diode is shorted , under 14.2 v the field is not grounding or a diode is open .
The alt output wire should connect to the start relay bat terminal , , 10 ga from there to the starter & minimum 4 ga , I use 1 ga welding cable to the battery  in the trunk .,
I hope this helps you

[YellowThumper]

Thanks Chryco P.
Your statement of 16v max rings a bell. Up until recently the v would vary.  Now my "steady" is 16v regardless of engine rpm.
As noted I am getting around 11.5 v. When testing the regulator wire.
Going to swap in another alternator to see if things change or remain.
From there (if not fixed) I will then look at rewiring.
Goody mentioned his is wired up being fed via a relay. I may try that route next.
In all of my changes to harness this far. I have many open feed lines available.
Does it matter if regulator line fed with switch on power while cranking or not?
Is the other wire a ground? Been trying to trace on wiring schematics.

Will try and jump in deep tomorrow to put this to bed once and for all.

Thanks.

[1 Wild R/T]

Check the voltage at the blue wire going to the voltage regulator..... If it is low the regulator will raise the alternator voltage to bring the voltage on that blue wire up & if it's lower than what you read at the battery that means the charge voltage will be higher than spec..... As far as an alternator topping out at 16v.... Sorry, I've seen alternators push upwards of 70 volts.... But the battery will typically blow up at around 18v.... And thats when the voltage really climbs because the battery is no longer soaking up the excess power...

[Chryco Psycho]

the regulator & lt field wire should be on the blue run circuit not the brown start circuit , you do not need the alt charging until after it is running .
The Blue wire feeds constant voltage , the green wire from the field is the ground which is switched by the regulator to control the alt output .

[TelisSE440]

You can eliminate the alternator question once and for all, if you could do this: Run a regular gauge wire directly from the battery positive post (need a looong wire though if the battery is in the trunk), to the voltage regulator, then cut the blue wire on the VR socket (somewhere to the downside so you can insulate it back together and not showing ugly) and connect the blue wire on the VR socket side with the aforementioned battery bypass, insulate the new connection and the remaining blue wire that goes back into the system. Start up engine, the voltage should be ok, if not, you should look for:

              1) Faulty alternator
              2) Faulty Voltage Regulator or not grounding correctly (i believe that's not the case)
              3) The green wire not wired correctly or rusted connections (i believe that's not the case either)

If everything is ok, then search for high resistance in the wires, it will be a little hard though. The ignition switches are notorious for the creations of such resistances (the blue ignition/VR wire goes through the switch and back using contact plates which rust over time), but they are very easy to check.

[TelisSE440]

I have attached a 1973 Challenger service manual (i believe it isn't different in that particular segment). You search for the ignition switch socket. Now to check the switch resistance: Check the voltage of the red wire (which takes current from the battery). Compare it to the battery voltage, if lower then you have resistance from that wire to the battery. Turn the key in "on" position. Then check the voltage on the blue wire coming out from the switch (ignition 1 wire, the one feeding the alternator and VR). If lower, then the plates inside the switch are corroded/faulty. Ma Mopar saw this switch problem (concerning overcharging problems) and suggests replacement of the ign. switch.

[YellowThumper]

Thank you Telis, Chryco P. and 1 Wild, Goody, and any others I may have missed.

So far I am surmising this issue is a combination of several problems.

1) I did check the blue in wire voltage with key on. It reads around 11.6v. The battery (in trunk) reads 12.5 give or take. All wiring feeds up  front all read same as battery.
2) Now as Chryco P. noted about the 16v maxing out. I felt it was worth a try and switched alternators out. Sure enough I now have voltage that will fluctuate based on rpm. Still too high but varies.
Alt was bad.

3) With that, I ran a temporary power wire from up front fuse block to the blue wire bypassing harness wire. Voltage is now much more reasonable. It pegs at a touch over 15v.
Even though it is improved with overall voltage it seems to be very erratic.
QUESTION:
As with this test I have only 1/2 way bypassed the v/r plug. Can I now just run the green wire straight to a ground and bypass harness altogether?

[TelisSE440]

QUESTION:
As with this test I have only 1/2 way bypassed the v/r plug. Can I now just run the green wire straight to a ground and bypass harness altogether?

You're welcome.
About the green wire, this wire is the other "end of the system", it's basically the ground. If you ground it, the voltage will go to the max and damage will occur. What the VR does is that it is sensing the voltage through the blue wire and then it "opens the door" to the green wire to ground from the VR metal body to the firewall. I may be wrong, but i can't relate an overcharging condition with a bad ground of the VR (or a green wire malfunction for that matter unless it grounds somewhere). But you can use a wire to connect the probe of the alternator where the green wire go, directly to the VR (green wire probe), the green wire goes through the harness directly on the VR. Warning: this wire mustn't touch any ground , it will top out the alternator output.

[YellowThumper]

TellisSE,
I understand what you are saying about the green.

Checking continuity I did just find that I had the green wire switched on the back of alternator. Been told in past it did not make a difference. Switched back anyway.

Fired it up again and it may be slightly more stable.
Going to add a separate ground wire to v reg mounting and this time use dielectric grease as well.

So close I can taste it.
I have sat idle with this since last years Van Nuys fling.

[YellowThumper]

Ok again. A huge thank you from me to all.
Here to report that all is now exactly as should be.
Rock steady 14.5 (probably slightly more). Thruought rpm range. Purposely dogged rpm and it will trickle down to 12+.
My anal retentivness played off a bit today. With all the previous power distribution changes made I had left extra feeds already wrapped in harness. Pulled one out and wired it up plugged in a fuse and ready to go. Nicely enough it was also a blue wire.
Added another ground wire connection along with dielectric grease for good measures. Short one from v/r and ground strap right next to it.

Only issue was some traction problems going into 2nd and 3rd.  Think that will be manageable...

Time to get it out frequently this summer now.


Mike.