Odd electrical Q

1980 gl 5 door ea81 [mod] 4w 4s. The external to internal vr [mod] was done prior to my having purchased the car. Now that i have done the 86 max [mod] a gremlin has arizzzzen. i have had the car for about three years without any dead bat problems until now. purchased a new 86 max alt and to make it all tidy, a new L,S plug. i think and ive checked several times that all the instructions were followed. The S side of the plug now has bat voltage all the time even with the key off and out. Um that drains the bat over night. Take the plug out, no bat drain. i have the 80 1600, 1800 service manual, nice, in the wire diagram the yellow S goes to the white on the 7 pin terminal where the old ex vr was. the book shows this wire going to the bat thru the now replaced fusible links. My question is not just how to fix this, but after 3+ years? and all i did was put in another, higher amp out, alt did this gremlin come out of its hole and now drain the bat of all its blood, yes i had to add water. i have another 80 30 over ea71 5s 2w i would like to put this alt mod into, but would like to do it correctly, thanks much for any good advice, and yes this is my first post as iv always been able to find the answer. i like this USMB