Yeah, 1v drop is pretty big. This is a common problem among all older cars, wire oxidizes and resistance increases, as resistance increase things heat up which further increases heat and can also cause wires to oxidize faster... vicious cycle. The old wire type fusible link used from '86.5 up to the mid '89 model is famous for causing voltage issues. It can be swapped with the sealed FL used later on.
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.
If you're so inclined I'm always more than happy to accept tips via PayPal. 
Tip Jar ---> 
|