Msd 6al install. Now over charging
- Thread starter Dan s
- Start date
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67Dart273
Well-Known Member
FIRST THING we need to know is WHAT YEAR MODEL are we working on?
You may have damaged the ECU modules because it was ALREADY overcharging.
WARNING: I am BIASED against "one wire" alternators, ESPECIALLY in a situation like this. "It might be" that it fixed the problem, or IT MIGHT make the problem WORSE, depending on what that problem IS
The most prevalent cause of over charging is VOLTAGE DROP caused by POOR CONNECTIONS in the wiring harness. These can be numerous and add up. The "popular" guys are the BULKHEAD CONNECTOR, the IGNITION SWITCH connector, the IGNITION SWITCH, and the AMMETER CIRCUIT
Other causes are (rarely) the voltage regulator, poor grounding at the VR or poor grounding between engine/ battery/ and body. Rarely, the battery itself
ANOTHER LARGE NASTY CAUSE on 70 and later cars is damaged/ broken brush holders which ground out the "green wire" brush and cause the alternator to charge "full output" regardless of the regulator
If you have not done so, go to MyMopar and download a free service manual, and also the aftermarket wiring diagrams in the wiring section. these diagrams are not always very complete or detailed, but can be easier to follow
YEAR IS IMPORTANT. Especially around 71/ later there were changes almost every year. 74 has the oddball "seat belt interlock"
You may have damaged the ECU modules because it was ALREADY overcharging.
WARNING: I am BIASED against "one wire" alternators, ESPECIALLY in a situation like this. "It might be" that it fixed the problem, or IT MIGHT make the problem WORSE, depending on what that problem IS
The most prevalent cause of over charging is VOLTAGE DROP caused by POOR CONNECTIONS in the wiring harness. These can be numerous and add up. The "popular" guys are the BULKHEAD CONNECTOR, the IGNITION SWITCH connector, the IGNITION SWITCH, and the AMMETER CIRCUIT
Other causes are (rarely) the voltage regulator, poor grounding at the VR or poor grounding between engine/ battery/ and body. Rarely, the battery itself
ANOTHER LARGE NASTY CAUSE on 70 and later cars is damaged/ broken brush holders which ground out the "green wire" brush and cause the alternator to charge "full output" regardless of the regulator
If you have not done so, go to MyMopar and download a free service manual, and also the aftermarket wiring diagrams in the wiring section. these diagrams are not always very complete or detailed, but can be easier to follow
YEAR IS IMPORTANT. Especially around 71/ later there were changes almost every year. 74 has the oddball "seat belt interlock"
It’s a 69. Originally a 273 car. It wasn’t over charging before. (That I know of). I did replace the alternator right after the first ignition module went bad. The reason I went through the msd stuff is because I was having a problem with the connection at the ignition module which caused me to think it was bad
I have had some problems with the switch. Some times I have to kinda jiggle it to get the gauges to work. Sounds like I need to start there.
I have had some problems with the switch. Some times I have to kinda jiggle it to get the gauges to work. Sounds like I need to start there.
67Dart273
Well-Known Member
Couple of "first tests."
To see if the regulator at least has some control (and not that the alternator field is grounding) With the engine running "fast idle" disconnect first, the VR connector and make sure it stops charging--monitor battery voltage with a meter
Next to double check, same thing, disconnect the green wire at the alternator
Just what does it run up to, voltage? Monitor battery voltage, bring up RPM. If it is say, 16 or below, likely a problem in the harness or bad VR. If it goes above that, likely something grounding the field, which causes full output
Voltage tests: Turn key to "run" with engine stopped. Probe ballast and find "key" side, which should be full battery. Now measure from there to battery POS. You are hoping for a very low reading, more than .3V or so (3/10 of one volt) is voltage drop.
I sometimes recommend for a somewhat "easy" work around is to add a relay to relief stress on that circuit. The "run" circuit is a wire coming out of the bulkhead --usually dark blue-- that supplies underhood "run" loads---the alternator field, VR, ignition, electric choke if used, and smog doo dads if used. Cut that wire ;and use the firewall end to trigger a Bosch relay. Feed the relay power in contact with a fused/ breaker off the starter relay big stud. Connect the engine bay end of the cut wire to the switched output
Also check ground side for drop. With engine running fast idle, make this check first with all loads turned off, and again with lights, heater, etc running. Stab your meter into the top of the battery NEG post. Stab the other into the metal mount flange of the VR. You are hoping for almost zero, which is perfect. again, any reading there above a couple tenths means voltage drop. Improve grounding between block, body, and battery
To see if the regulator at least has some control (and not that the alternator field is grounding) With the engine running "fast idle" disconnect first, the VR connector and make sure it stops charging--monitor battery voltage with a meter
Next to double check, same thing, disconnect the green wire at the alternator
Just what does it run up to, voltage? Monitor battery voltage, bring up RPM. If it is say, 16 or below, likely a problem in the harness or bad VR. If it goes above that, likely something grounding the field, which causes full output
Voltage tests: Turn key to "run" with engine stopped. Probe ballast and find "key" side, which should be full battery. Now measure from there to battery POS. You are hoping for a very low reading, more than .3V or so (3/10 of one volt) is voltage drop.
I sometimes recommend for a somewhat "easy" work around is to add a relay to relief stress on that circuit. The "run" circuit is a wire coming out of the bulkhead --usually dark blue-- that supplies underhood "run" loads---the alternator field, VR, ignition, electric choke if used, and smog doo dads if used. Cut that wire ;and use the firewall end to trigger a Bosch relay. Feed the relay power in contact with a fused/ breaker off the starter relay big stud. Connect the engine bay end of the cut wire to the switched output
Also check ground side for drop. With engine running fast idle, make this check first with all loads turned off, and again with lights, heater, etc running. Stab your meter into the top of the battery NEG post. Stab the other into the metal mount flange of the VR. You are hoping for almost zero, which is perfect. again, any reading there above a couple tenths means voltage drop. Improve grounding between block, body, and battery
67Dart273
Well-Known Member
I also forgot to mention your MSD. Msd main power, the "big black" and "big red" should go to a good ground and the red straight to good battery power, NOT the ballast connections
The "small red" is a power on trigger wire and should be connected to the old ballast connections. "It might be" that they are not too well made, so check that
The "small red" is a power on trigger wire and should be connected to the old ballast connections. "It might be" that they are not too well made, so check that
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Rat Bastid
Dunamis Metron
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