I agree w/ Alan in that the #2 sensing wire registers the voltage being used @ a location where the power is distributed from. There is a slight voltage drop because of the distribution to all accessories drawing power after the key is turned to ON/RUN, @ any given time. This constantly changes during load draws from radiator fans, A/C, electric windows, heater, heated seats, etc. If the #2 wire were attached directly to the BATT lug on the alternator (what 3'' long) the alt. would always sense high voltage w/o a drop.
I don't see the #2 wire connected to the BATT term on the key switch. Shouldn't the #2 be connected to the 'ON/RUN' post. I'm going to have to go look tonight @ my key switch and wiring diagram @ home.... more &/or a correction tomorrow. But if I think about this my power lead to my key switch goes to the OFF post. Once the key is turned it provides a connection to either ACC, ON/RUN, or START posts.
Some set ups (which have a key start position, 4 post key switch) would wire the #2 wire w/ a diode.??? ... yes?? to the ON/RUN post??
imput anyone.....
AND
I realize others have a simple 2 post key switch and a foot start. Then I could see having the diode in place on the RUN post. But if (say Alan has a V8 & probably a 4 post [[acc,off,on/run,start]] key switch in his truck) then the #2 sensing wire would be connected to the ON post. I have a 6'' jumper wire from the 'ON/RUN' post to the 'START' post as all the start does is provide power to the starter solonid for a couple seconds & using the 'ON/RUN' wire for that purpose.
