Here's the situation, my 98 stang GT is showing really low voltage, almost in the red, my electric windows take forever to go up or down (not sure if this is related to the problem or not), but it just started doing this a month ago, exactly when my car started to overheat on me. I had the alternator tested, results are that it's good, I put a new serpentine belt on. and had the battery checked.. all good. The car only overheats if I'm in stop and go traffic, never while I'm highway driving of course.. My real question I guess is "Can the low voltage be the culprit as to why my fan don't seem to be keeping the engine cool?" This has been bugging me for awhile now. and it all happened at the same time.. does anyone have any ideas before I have to take it to the shop and spend lots of cash on this problem?

 

Yeah seems your fan isn't being powered up enough to cool the engine at idle! The low voltage could be part of a computer problem although it seems more like a ground or bad connection at a terminal. I would pull off the ground strap that bolts to the motor and clean it up with a wire brush. Do the same to the power wire that bolts to the box just beside the battery (this is where the alternator goes, there should be a jumper wire from there to the battery)

 

when you tested the alternator. did you test it just for voltage? it should have been checked to see how many amps it is able to generate. still sounds like an alternator problem although there maybe a bad ground somewhere. also check the battery terminals if they dont have good connection the alternator will not properly charge the battery.