Dave,
""In your experiment the engine was not running and the voltage was at 11.9. Given that the VR is designed to keep the system at 14.5V, it makes sense that a higher voltage would be presented on the field circuit.""

* Is it normal for BOTH field wires to show 14+ volts or would one field wire show it and the other would not?
Thanks


Danny,
That does not sound crazy and that is exactly what I am going thru. Thank you.


Before I tested adding the diode, I rechecked my voltages again with the key in the RUN position and the engine off. I once again found 14.5-15.5v at "both" of the alternator field connectors while just 12.0v at the battery and 11.9v at the MSD SMALL RED (CRANK/RUN) wire. At the least I am only losing .1v from the battery to the MSD box (CRANK/RUN) connection.

Then I added the diode (400v/1.5a, this does not allow feedback into the CRANK/RUN circuits) on the MSD SMALL RED wire last night and I made some more tests. Now with the key at the RUN position and the engine off, I was getting a voltage reading at the alternator BLUE wire of 11.9v and the GREEN wire of 1.1v. I could not get a reading of more than 11.9v at the BLUE wire after three different attempts (shutting off the key, waiting a few mintues, then testing again). I did not get a chance to start the car but at least my voltages are down.

The theory here is that the Street Fire box (economical street box) may have feedback thru the SMALL RED wire that is connected to the RUN/CRANK 12v feed wires that lead to the key. (Maybe the MSD 6 and 7 boxes do not do this) The key is also connected to the alternator field wire thru the BLUE/WHITE TRACER wire. If the MSD SF box is "leaking" due to the internal capacitors, then it appears that the voltage could be affected all the way back to the alternator. This is why I am testing a diode on the MSD SMALL WIRE to keep any "leaking" from exiting the MSD box and into the CRANK/RUN wires. (see attached)

Note: MSD suggested that I upgrade my current 40 year ond ammeter and my cheepo inside voltage gauge to new Autometer units. MSD said that they talked to Autometer about this which resulted in this suggestion. I wonder if the Autometer gauges already have diodes in them to keep the feedback out of the gauges.

I also made a continuity check on the MSD LARGE RED wire to the MSD housing and got a 0.0 reading. So that looks good.


I won't be able to start the car for a while due to our weather but I just want to see if the battery/alt voltage drops down from 15+ and also to see if the ammeter fluctuation changes.

It is a shot in the dark but I want to try it.

Thanks for the replies.