Going crazy with new Duster and over voltage issue.

ultimatejay said
Although i did notice there is no ground cable from block to firewall. There is a small ground off main battery ground that goes to front radiator support. I assume this is the ground for the chassis or is there supposed to be another from engine to firewall?

My recollection is the body grounding changed areoun 1970. Early cars had battery to engine, then engine to firewall on the passenger side. Around '70 the battery negative also got a a 12 ga ground to body.

ultimatejay said
I tested field wire to positive battery cable with key on engine off and had 1.2 volts

On a '70 you must measure the blue field wire. Another place to check is at the ballast resistor blue wire connection.
Assuming you did that, then yes too much resistance as explained earlier in this thread.

ultimatejay said
When i check voltage at ballast resistor i get the same voltage on both ends.

It will be the same when there is no current flowing through it. Voltage only drops when current goes through a device or a poor connection.

For example, if there are three light bulbs connected in a row to a battery.
When the switch is open the voltage in at any point will be battery voltage.
Close the switch, and voltage will be lower on the other side of each bulb. After the last bulb the voltage will be zero.

ultimatejay said
Also with key on and testing voltage at ignition lead to coil Im getting 12v

See above.

ultimatejay said
This means the ballast resistor is bad correct?

No.

ultimatejay said
Also, would this cause the high voltage charge issue?

See the explanation from 67Dart273. This is the main point.

hotrod swinger said
If you measure a 1.5 V drop, this may give you a charging voltage of ~16 V because the voltage regulator will think the system is running 1.5 V lower than it actually is.

This schematic shows the main circuits of interest.

The main splice (black dot) connects the two power sources to the wires feeding everything else.
The battery provides power at most, at 12.8 Volts
When the alternator is running, it provides power at 13.8 - 14.8 Volts.
Any and all resistance to flow between the alternator output and the regulator's sensing terminal (connects to wire J2B) will cause over the regulator to atttempt to up the voltage.

Observe the ammeter too. It shows current flow in or out of the battery, fo amps out to 40 amps in. Straight up is zero. That's where it should be after recharging the battery.