Electrical question about a 1968 300?

I've had my deceased Uncle's 68 300 for about 20 years. I guess you could call it survivor type car although he managed to bang it up a couple of times before he passed on. Anyway here's the question. Last year when I had it out for the summer I noticed the alternator gauge would flicker over to discharge occasionally. This summer I got it out and it is sitting on discharge constantly. When you apply any accessory that uses power it drags further over into the discharge zone. I've changed the alternator and checked the ground off the battery and all seems fine with that. I much more familiar with 70 Mopars and I don't even see what appears to be a voltage regulator under the hood of this 68 C-body. Anyone have any ideas what I should try or check to solve this problem? Electrical is far from my strong point!

The VR is a small box with one wire on each end.Get one of the new replacement ones that electronic.It bolts in and wires up just like OE.That way you dont have to run a new field wire and change to the new style alt and new style reg.It should be on the firewall IIRC.Its about 2 inches by 1 inch and if OE about 1 inch tall.Rocky

What Rocky said. And when you mount the new one make sure there's good contact between the case/mounting bolts & the firewall (get some bare metal showing there).

Don't forget to check the bulkhead connector. The amp gauge wires pass through it and can cause some heat problems. Corrosion can cause erratic fluctuations in the system. You can see the heavy red wire for the charging system here.
This is a shot of my 68 New Port. It's kinda cruddy but I haven't got to the engine bay yet. This will be next as I am about to install all new brake lines and a new master and booster.

A new electronic regulator. This one is Chinese. I imagine you could find one built here in the States, but I got a deal on this. So I'm gonna take that chance. Please keep the hate to yourselves folks.

Most of the new regs are real flat and dont have the tall box cover like that.You can put your old cover over the new one if looks are a concern.Rocky

Thank you for the advice and photo. I cleaned the bulkhead terminals yesterday and while they were corroded it didn't fix the problem. The car still goes to discharge as soon as I start it. I ordered up a new V-R and will probably try getting that on if its a decent evening tomorrow when I get off work. Hope that does it, I had put a tester on the battery and it just sits at close to 12 volts whether the car is running or not. Maybe the dang new alternator is garbage, wouldn't be the first one that was lately. Picture of the "beast" in case anyone likes C-bodies.

With the eng on a fast idle and all lights/accessories OFF then take off the green wire from the alt field terminal & jump 12V from the batt positive terminal to the male terminal on the alt that you just removed the green wire connector from & see if it charges. Keep the jumper on there for 3 seconds max just long enough for you to look at the meter & get a reading & likely you'll hear the eng slow down slightly as the alt engageing from this "full fielding" will drag the eng speed down slightly but enough to notice. this'll tell you the alt is good/brushes have continuity

Thank you to all that answered. I have tried all of the above. Alternator tests ok, new voltage regulator, battery tests ok, power to the fuse box on both side of each fuse, cleaned the bulkhead connections...still goes to discharge upon starting. Anyone have any other ideas? I never grew up wanting to be an electrician...possibly a high voltage ground, or the gauge itself? Where would you guys start looking? Any other ideas would be great!

this is the OE 1968 (early) system with the box reg in the pic & an alt with either 1 field terminal (69 & earlier) or a later alt with 2 field terminals & if so then one of them has to be grounded right there to the alt case. With the alt/reg good (assuming the reg is grounded well to the firewall) that only leaves the field wiring. check that there is fire to the blue wire (ign) side terminal on the reg with the key on or jump fire directly to it from the batt positive terminal or the starter relay large "batt" stud & see if it will now charge. If not switch the ign off then take off the green wire off of the other side of the reg and on the other end of the green wire at the alt pull the female connector off of the field terminal & connect the two with a jumper wire & restart it & see if it now charges. If the alt is good & has 1 field terminal with the green wire on it or 1 of the field terminals grounded if it's a later alt & the reg is good & the reg is grounded and the "ign" side of the reg has fire and there's continuity between the reg "fld" terminal and the alt field terminal via the green wire then it MUST charge. Holler back when you can. EDIT To check the continuity of the green wire an easier way would be (ign off) to disconnect the green wire from the reg "fld" terminal & then start it & jump fire to the green wire (not the fld terminal) for 3 seconds max & see if it charges (fast idle)

You wouldn't have the battery in wrong would you ? lay a screwdriver up against the back bearing of the alt and see if there is a magnetic field there. if the driver don't "stick" to the back of the alt , its not charging even though the alt may be good . if the batt was installed reversed u will have some electric issues including fried wires etc.

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this is the OE 1968 (early) system with the box reg in the pic & an alt with either 1 field terminal (69 & earlier) or a later alt with 2 field terminals & if so then one of them has to be grounded right there to the alt case. With the alt/reg good (assuming the reg is grounded well to the firewall) that only leaves the field wiring. check that there is fire to the blue wire (ign) side terminal on the reg with the key on or jump fire directly to it from the batt positive terminal or the starter relay large "batt" stud & see if it will now charge. If not switch the ign off then take off the green wire off of the other side of the reg and on the other end of the green wire at the alt pull the female connector off of the field terminal & connect the two with a jumper wire & restart it & see if it now charges. If the alt is good & has 1 field terminal with the green wire on it or 1 of the field terminals grounded if it's a later alt & the reg is good & the reg is grounded and the "ign" side of the reg has fire and there's continuity between the reg "fld" terminal and the alt field terminal via the green wire then it MUST charge. Holler back when you can. EDIT To check the continuity of the green wire an easier way would be (ign off) to disconnect the green wire from the reg "fld" terminal & then start it & jump fire to the green wire (not the fld terminal) for 3 seconds max & see if it charges (fast idle)

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ground one field most replacement alts have both field terminals isolated and one needs to be grounded. the original would be internally grounded at the screw .