You could look at Bob Nuckolls's wiring diagrams at aeroelectric.com and talk to him on the aeroelectric maillist. I have his automotice alternator  overvolt "crowbar" protection circuit installed. Basically, you put the alternator field through a contactor which is activated by a switch, and deactivated by a 5a breaker if overvolts are sensed.

John Slade

Thanks John.  I’m familiar with electric Bob’s info.  I had his crowbar device on my RV-8, which had an externally regulated alternator.  I considered installing his internal regulator version on the RV-3, but just couldn’t justify the effort.  I have absolutely NEVER heard of a modern alternator causing damage from overvoltage, so I figure the risk is minimal.  Worst case, the EM-2 tells me I’m overvoltage, and I shut off the master.  That will allow the overvoltage to continue on the non-essential side of the buss, but I can turn off the radio and transponder to save them.  There really isn’t anything else of significance to worry about.  I’m still considering my options, but at the very least, I’ll get rid of the current switch for the excitation current.  No good can be done with that switch.  Of course, since it’s there already, I could use it to power a dedicated alternator contactor.  Decisions, decisions.  BTW, I can hear Tracy mentally grumbling about the thought of adding any other component :-)

Rusty