1973 Dodge Charger Rallye - Over-Charging / 4-pin Ballast issue? Wiring issues!!!


Asked by Aug 12, 2014 at 05:40 PM about the 1973 Dodge Charger

Question type: Maintenance & Repair

Wiring issues here!! Restoring a 73 Charger Rallye (came w  electric ignition, 4 prong
ballast on firewall). Car had some major shorts at bulkhead, but is now starting and
running after removing the "Amp Meter" circuit & connecting the alternator output
directly to the starter relay. Ran new volt meter under dash instead. At same time,
bypassed the main hot lead through bulkhead with an independent 8ga wire through it's
own new firewall grommet. Had to fix a few melted wires that these two wires came in
contact with under dash & shorts now seem to be resolved... I couldn't find any 10ga
fusible links, so running a 40A fuse on the main hot wire from battery to firewall, and
currently am NOT running any fusible link/fuses, etc. between alternator & starter
relay... now that you know the history, here's what it's doing:

Voltage at battery kept climbing and I would finally have to shut car off when it spiked
over 17v.. It was popping these 40A fuses constantly and also blew a few voltage
regulators. Prior to me working on it, it had previously blown a coil and also the ignition
control module. Now that we've resolved the shorts (best I can tell), I'm pretty sure that
the 4prong ballast was flip-flopped. Apparantly it's been wired like this for over 20 years!
It was getting full power to the leads going into ballast, and the brown wire going to coil
was ALSO getting close to full voltage (about 12.6 when battery was reading around
12.8-12.9). The (+) lead going from ballast to the alternator WAS NOT getting full power
(was reading about 11.4v). I read enough to find that the coil should have the reduced
voltage, and the alternator should be getting the bat voltage, so I flipped the resistor
around and now the alternator (+) is getting the 12.6(ish) to its lead, and the tan wire
post to coil is now getting the 11.4v... So far after flip-flopping the ballast (and replacing
ANOTHER) voltage regulator, the car is running and not blowing the 40A fuse anymore,
but when I hook my volt-meter to the battery, it shows to be charging at around 16
VOLTS at high idle! The voltage regulator is keeping it from going much above 16v, but
that seems REALLY high. Wierd thing is that the new volt-meter under dash is showing
barely over 14v. Is there something that I'm missing here? I'm not totally sure that
flipping this ballast is correct or not, but according to what I've read it was a good
educated guess. The plugs have prongs that only allow them to plug in in 1 direction,
so there shouldn't be too many variations until I can get this thing right! The side with
the notch in it currently has the wire that loops from top to bottom on the 2 prongs, (left
hand side if your facing it from front of car). The right side has the tan lead on the
bottom prong that is showing 11.4v (going to coil)... Could this ballast be the issue?
Can't find correct Ohm specs for this ballast or volt specs (prong for prong - for
dummies!) anywhere to use as a guideline.. If ballast specs sound correct, why is it
charging so high? Could a fusible link on the alternator wire add extra resistance to
slightly lower the voltage? I don't figure I should have to put a "capacitor" on the
"alternator-to-starter relay" wire, so I'm pretty sure I'm missing something!... Slightly
clueless on this one so any help appreciated!

I have a couple of other issues besides this, but this charging thing has me stumped!
Dash lights don't seem to work, temp gauge & oil pressure gauge don't work! (bought
new sending units but haven't installed yet). Also, we installed a new headlight switch
throughout all of this, and everything functions as far as high/low beams, brakes,
running lights, signals, etc.. but when the headlights are off (even if ignition is off), if you
twist the switch (to brighten/dim the interior lights), instead of fading the interior lights,
it greadually turns the running lamps on!!! There was one stray purple wire that wasn't
in the connector, and I thought I put it on the same post it came off of when re-
installing, but it's very possible that I may have connected that wire on an incorrect
prong or that it came out of the original connector.. not sure.. still have to check that
out after I fix charging problem!

1 Answer


Think I got this figured out this weekend (at least most of it!) Hopefully this helps someone else if they run into the same issue! The main problem was that my field voltage going to alternator was almost 1v lower than true voltage - causing VR/alternator to think it needed to charge more. A simple fix would've been to add a switch relay and provide full power to this wire, but preferred to find route of the problem... After all of this, I'm thinking I probably should've just done the "fleet fix" - would've been WAY easier (if your wires aren't already melted like mine were!)! "Fleet fix" = Run a black 8ga wire from charging post of alternator through new grommet in firewall to black wire (#18 @ bulkhead in diagram), then run a red 8ga wire from (+) battery terminal through new grommet in firewall to the red wire (#16 @ bulkhead in diagram). Be sure to add at least a 40a fuse to the red wire and an "amp appropriate" fuse or fusible link on alternator charge wire if you do this (50A mega fuse or Maxi fuse should work for most if you don't have the larger 100A or 120A alternators) - This will save you LOADS work later if you have an overcharging melt-down like I did!! They also sell waterproof automotive "breakers" at most autoparts stores that would prevent going through fuzes if you have a really bad problem w high voltage. Anyway - back to my repair...#################### Both my red & black wires were melted, as well as several other wires in the main harness... Because of this, I chose to update the wiring & go with the "90's style" alternator/charging w aftermarket volt-meter setup. So... I added new grounds from motor to frame & motor to body. Also ran a new ground from Alternator to firewall (same place motor ground is attached to firewall). This got the charging voltage down from close to 17v to about 16.5v.. Since we bypassed ammeter, new 8ga wire was ran from alternator to starter relay. I had the main hot battery lead going from battery terminal through firewall - bypassing bulkhead and spliced into the RED wire (#16 @ bulkhead). Black wire (#18) under dash from Ammeter was completely cut and circuit removed from bulkhead junction all together. #################### Found 2 problems here! Problem #1 - The red wire (#16) is the OUTPUT wire from Ammeter & originally went back to the (+) battery terminal! The black wire (#18) is INPUT. If you follow the black wire further up the harness (closer to the gauges), it splices into 3 OTHER wires in a solder joint... After noticing this, I switched my hot lead from the #16 red wire (ammeter output) to the #18 black input wire at the 3-way junction. Since I couldn't reach back of ammeter, I terminated the red wire & taped it up since it was still hot from the feed through ammeter. Ammeter not reading anything now, but that's expected. Will be pulling instrument cluster later to replace blown bulbs, relay & any gauges that didn't make it through all this... Will either complete ammeter circuit and run another wire back to battery from Ammeter, or just completely remove remaining ammeter wires to make sure no possible shorts. If ammeter won't be used any longer - may add a tachometer in it's place if I can find a clean way to make that happen while I have the instrument cluster out! #################### Problem #2 - I found that voltage was about .5v higher at starter relay than at (+) battery terminal when engine running. Since my main hot wire was ran to battery terminal, this voltage was also being reflected on my alternator field wire - showing lower voltage than it should (which makes it charge more!). I cut the main feed circuit from (+) battery terminal, and ran it directly to the same starter relay post that alternator charge going to. This helped a bunch! Now I was getting closer to proper voltage on my alternator field wire. This got the charging voltage down to about 15.7v. Still too high, but at least now I know that all battery voltage is coming from one clean uninterrupted circuit. #################### 15.7v is still not acceptable, so did more probing with volt-meter & found that inside the car when the door was open the BAT voltage was jumping up to almost 15 volts (key on engine OFF!) = ANOTHER short!!! Not sure why the voltage was going higher than battery voltage - didn't even know that was possible, but it was! You could literally push in the door switch, buzzer turns off, and simultaneously, the voltage drops from about 15v back to 12.__v and when you let off (open) - buzzer back on, voltage jumps to abt 15v! One of the buzzers is actually inside the horn relay @ fuse box - the other is under passenger side by glove box. To be safe, we disconnected both! We pulled the horn relay/door buzzer (same piece) and the voltage stayed within 0.1v of battery voltage regardless of door open/closed. Horn relay actually rattles like a maraca, so pretty sure it's toast - and probably is the cause of short, but could also be the switch at door.. I couldn't find the door buzzer on the wiring diagram, so will have to trace this down, but know that when the horn relay is pulled - problem is gone. Part # for the horn relay (according to Dodge) is part #3588358. I also found it as #3579204, 3579205, 3513206 & a few others. Anyway - after removing that relay voltage is now g2g! To be safe, I also replaced the brittle field wires going to alternator. Now charging at around 13.8v. The only gauge that works on the dash is the new volt-meter and the fuel gauge - hopefully just a blown dash relay or bad sending units, but can figure out/replace as needed now that we have the high voltage problem fixed!!

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