Alternators 1 Wire or 3 Wire ( That is the question!)

[fabr]

Welllll,it's a long read but welllllll worth the effort. 

http://www.madelectrical.com/electricaltech/onewire-threewire.shtml


 I am finishing up wiring the car and when it came time to run the alternator circuit I find myself in a quandry. I'm using a 1 wire , alternator field break type of battery disconnect (4 terminal)switch. I'm hit with the reality that the alternator being a 1 wire is not going to have a field wire to tap into.  Well,fook,that doesn't address the need to open the field wire circuit to stop alternator output before battery disconnect in an emergency situation allowing the alternator to back feed the electrical system which would allow the engine to continue running. Hooking up the alternator battery charge wire to the terminals doesn't do a damn thing to prevent back feeding and it will be carrying a lot more amps than the small terminals circuit can handle anyway.

Oh well,after reading the above,I now understand the practical differences in performance of a 1 wire vs 3 wire alternator. I'm very glad I learned a lot today. The 1 wire polished alternator is going to my buddy,the electrical motor rebuilder tomorrow to be returned to a 3 wire unit. Never a wasted day when I learn something ,actually quite beneficial.

[BDKW1]

Run the trigger wire with a relay, prevents back feeding and run on.

[fabr]

My understanding is that that is done but may not actually serve the purpose since that would only effectively cut the field/trigger at the same time as the battery cut and could still allow run on/backfeeding.

[dsrace]

well i think the article states the best case to go to the 3 wire!

[fabr]

The ability to remotely sense voltage so the alternator delivers full power to the main junction is the best benefit.

[fabr]

I should add that not all alternators voltage regulators have access to the field wire.  All ,SFAIK,have the s terminal allowing remote voltage sensing.

[DeepBusch69]

Well I finally got the article read.  Interesting, never thought it out that deep.  But just by luck, my buggy is wired the correct way.  My last VW buggy wouldn't shut off because the alt wire back fed the coil thru the idiot light.  A diode fixed that issue. 

Do you have an estimated date for firing the buggy up? 

[fabr]

Not really,all the fuel line pieces will be here hopefully Fri/Mon.. Hoping for it to be/should be within 2 weeks.