i have an electrical issue and i don't know where to start....

i put in a rebuilt alternator about a month ago, also a rebuilt ihkrI 'sword' a little earlier as i had a burnout there... not sure what caused it.

the charging system works well except with the blower fan on max ('4') or the rear defogger activated... using the obc test#9 the system voltage goes as low as 11.5 with these activated (car idling), otherwise never below 13.3 and as high as 14.7 no matter what else... i'm wondering if this would be symptomatic of a bad ground somewhere as i suspect the alternator is good. (belt is tight, btw and the terminal connections are good afaicantell i redid them again just in case)

i am still wondering what caused the fry-out at the ihkr it melted pretty bad... everything works well though, rear defog included... the ground wire leading to it is pretty heavy duty guage so a lot of current must pass through there... maybe my wiring fix is bad there but i don't think so.

i would be very interested how much the rear defog affects the system voltage on other cars, also if the top blower has an effect. thanks!