Alternator Overcharging, Blue Wire with Stripe 1972 Charger

[Tom Patchett]

Problem is that since owning this Charger, have had a constant battle with overcharging the electrical system. It caused me to burn down a battery on Power Tour in White Plains, Georgia. Decided to fix it. Normal driving was showing 16.5 volts as confirmed by testing. Would turn on the cabin fan to lower the voltage or in some cases the lights. Was getting about 9 months per battery.

Traced the problem easily to the positive wire going to the regultor on the fire wall was showing as a ground. Would read a constant 2 ohms on the multi meter. Then traced it past the bulkhead connector into the cabin. So far, easy. Got complicated.

You can skip this part, but let me explain exactly what vehicle am working on. This is a 1972 hardtop charger. It has factory air, Big Block, auto, ralleye dash, hide away headlights. Have rewired the power feed from the alternator to the starter relay. The distributor is an electronic MSD and the ignition 1 and ignition 2 wires are joined together. The regulator is a mopar 2 wire on the firewall.

Back to the wiring. The blue with white stripe is a hot feed that goes many places. As I am lying under the dash checking various items, decided needed more access and pulled the dash. Not the best idea.

Now had a real rat's nest. Nor could the errant grounding problem be found. Upon a couple of friend's advice looked to eliminate unnecessary relays and systems until it cleared

Soultion: Clip blue wire with stripe at the seat belt relay behind the glove box. Problem has vanished. Blue wire with stripe is testing good. Not an elegant solution, but a solution. Just fixed it this morning.

 

[LowBikeMike]

If you didnt have both ends of the wire disconnected when checking it for grounding your reading is inaccurate. You are reading the ohms to ground thru the device the other end was attached to and the 2 ohm reading was probably normal.

 

[Tom Patchett]

Blue with white stripe was isolated. Read 2 ohms. Not plugged in at field or at regulator. Why I started tearing into the wiring.

 

[Nacho-RT74]

The relay on pic is the hideaways relay. Althought it should be around there also the seatbelt warning system relay which of course is also sourced by this circuit.

Need to let you know the blue with white wire trace is the ign1 circuit, which also feeds the brake light bulb into the cluster, so a 2 ohms reading could be simply a bulb resistance, which will be pretty much normal being a bulb is a controlled short to ground device with low resistance. Of course, the seatbelt light bulb is another device feeded by this circuit.

This of course if emergency brake is applied &/or seatbelts are unfastened along with transmission in P or N

 

[Nacho-RT74]

On a side note, voltage doesn't charge a battery, amperes do. Overvoltage will kill any device designed to work on a voltage rate, but the amperes can't be pushed in, they are required by the device ( a bulb, an electric motor, a discharged batt ). So you can get an overvoltage rate and still get no charge.

 

[Tom Patchett]

Nacho, thank you for identifying the relay. My problem might not be solved. Have now lost my headlight door operation? Guessing need to replace that relay or one it feeds.

The alternator is now charging correctly. Showing about 14.5 volts.

 

[Nacho-RT74]

Dunno what you exactly made to the relay to need to be replaced, but if you need to replace, since original NOS are hard to find and expensive and reproductions are not anymore available you can use a 5 pins “bosch” relay to replace it. There is also a Ford or Gm relay option ( can’t recall the PN at this moment ) which you could use too and is not expensive. The advantage of the Ford unit is it gets chassis grounded, while the bosch relay needs to get the ground wired.

if you just cut the blue wire, just will need to reinstall it and done.

The seatbelt relay is this, and I think you already have it removed. I can see a 3 way plug loosen there hold by couple of cable ties

 

[Nacho-RT74]

Standard Motor products RY8 is the pn for an optional relay.
Would need to reuse the breaker attached to the relay… or get a new one, for protection of the system.

 

[Nacho-RT74]

well, checking the pic closelly it seems you cut this blue with white trace wire ? ( yellow circled )

IF SO... and trusting on this diagram ( 71, not 72 thought, but should be aprox the same with minor differences ) you could have cut any of these ends ( pointed with yellow arrows ), and that won't allow even to start and keep running the engine LOL... unless there is some jumper or modification along the ign circuit somewhere

 

[Tom Patchett]

Thanks again Nacho. Runs fine, I call it a retro mod.

Wiring would most likely be easier to work on if it was stock. Will certainly use your advice on the relay. Oddly enough, gained some electrical functions when I cut the wire to the headlight relay. The buzzer for key in and lights on started working, the brake fail warning light activated. Best I keep looking at my electrical. Know have grounding issues with turn signals.

 

[Nacho-RT74]

Something smells fishy on your wiring if everything keeps working after cut that wire if we trust on diagram LOL

 

[Tom Patchett]

You are so correct. Sometimes I laugh and then there are other times. Have owned this ride for 4 years, It has seen many different garages and people work on it before I ever owned it over the years. Believe at one time back in the day it was a $500 car.

Thank you again for the help, am ordering a RY-8 relay today.

 

[Nacho-RT74]

this is a diagram I made loooong time ago using the bosch relay

The RY8 relay got this diagram on his body

Terminals are numbered like this

prong 1 would take the place of the 86 Bosch prong on diagram
prong 2 would take the place of the 87A bosch prong on diagram
prong 3 would take the place of the 87 bosch prong on diagram
prong 4 would take the place of the 87A bosch prong on diagram

No wire ground required because RY8 takes ground by chassis, which bosh relay doesn't

Will need to get also the plugs, available at many electrical suppliers

More info here

https://www.allpar.com/threads/1971-charger-concealed-headlamp-motor-relay-alternative.222393/

Still dunno why you need to replace the relay... aren't hideaways working ?

 

[Tom Patchett]

The volt gauge is now showing 14.5 volts charging with the blue wire clipped off to the hideaways. Would like both the hideaways working, which they were, and the charging system not overcharging. Hoping by replacing the relay, this solves it all.

 

[Superbee82]

well, checking the pic closelly it seems you cut this blue with white trace wire ? ( yellow circled )

View attachment 1133340


IF SO... and trusting on this diagram ( 71, not 72 thought, but should be aprox the same with minor differences ) you could have cut any of these ends ( pointed with yellow arrows ), and that won't allow even to start and keep running the engine LOL... unless there is some jumper or modification along the ign circuit somewhere

View attachment 1133341

Where could one get this manal

 

[Nacho-RT74]

Where could one get this manal

Factory service manual... or FSM ( abreviated ). at MyMopar.com there is a section where you can download it for free, but I allways preffer the real deal, a paper book... even better if original used one.

CD or reprints allmost everywhere. quite often originals also float on ebay