Electrical issue

[Pparr]

Probably posted this in wrong place previously, but my voltage indicator in my 74 Roadrunner is showing discharge. I take off the battery cable it dies. Tested alternator, it's ok. Changed voltage regulator, problem remains. Any idea here?

 

[Yatzee]

Probably posted this in wrong place previously, but my voltage indicator in my 74 Roadrunner is showing discharge. I take off the battery cable it dies. Tested alternator, it's ok. Changed voltage regulator, problem remains. Any idea here?

Voltage gauges don't show discharge, amp gauges do. Alternators won't put out power with the battery disconnected because it needs 12 volts to excite it. Put a voltage gauge in that comes off the fuse panel main supply and check again.

 

[davek]

Did you check the bulkhead for a short or burnt wire? How did you test the alt?

 

[dan juhasz]

Check the heavy lead from the alt to the bulkhead connector, terminals love to burn off

 

[Shorthorse]

Voltage gauges don't show discharge, amp gauges do. Alternators won't put out power with the battery disconnected because it needs 12 volts to excite it. Put a voltage gauge in that comes off the fuse panel main supply and check again.

Yatzee, are you sure about that? Race cars that are required to have a battery cutoff switch will continue to run if the car runs an OEM style charging system and the disconnect switch does not interrupt the field wire also. Improperly wired cutoff switches (main battery feed only) will allow the engine to continue to run because the spinning alternator is supplying the 12V. Anybody that's ever failed tech inspection will attest to that.
It sounds to me like the ignition is running off the battery and the alternator is not producing any output or whatever output it has is not making it way into the electrical system.