1990 Mustang GT electrical problem

I couldn't be anymore frustrated. I went to go troubleshoot and it ended up to be the worst. First I started off killing a whole Optima Yellow Battery overnight this led me to know that I had a short somewhere. So I went to find out, attached the positive lead to the terminal and a light tester to the negative, attached the other end of the light tester to the chassis and it lit up! I went through all the fuses pulling them in and out and I found the fuse 8, when pulled made the light dim more ???... I took my multi-meter and it went from 5.6 amps to 4.2 amps, so it was not the solution... The whole car is grounded with + / -, what a joke... Don't know where to begin. Took all my aftermarket stuff out (stereo, alarm, and foglights) and were not the problem. I read up on something and heard how the alternator wire leads sometimes melt and short, but maybe someone else has experienced what I have. I have torn out and tested my electricals beneath the steering column, but everything still is lit. I believe it is something in the engine bay. Help would be most appreciated, atleast my car is not necessary to get me to work since it has a possibility of getting towed since BMW doesn't have its own parking, SOBs.

I have experienced this problem with bad diodes in the alternator.

Can you be more precise for someone that doesn't know too much. Are you saying I need a new alternator or can you suggest where I might get a new part to fix the problem? Should I try disconnecting my altenator somehow and see what it does?

Unfortunately it wasn't the alternator, replaced in and no luck :-(... I could have sworn it had theoretically been narrowed down to that because it seemed to be fine when I unplugged it... I am so lost and bought an alternator I didn't need.

Unfortunately it wasn't the alternator, replaced in and no luck :-(... I could have sworn it had theoretically been narrowed down to that because it seemed to be fine when I unplugged it... I am so lost and bought an alternator I didn't need.
Kris


I work with a lot of guys that do rebuilds and have shorts or open circuits on there cars,and I have had good luck with the method that you started with ,that is to pull fuses one at a time until current drain is gone,the thing to remenber there are some current flows that are ok ,radio memory cloclk ect.But non of these should pull the battery down.also if by pulling all the fuses does not clear the short than it is in the non fused cable and or wiring coming from the battery,unplug one at a time to isolate short or ground .Take your time and go back to repeat
this process,it may take several times of going through it.

If I can be of further help let me know Dave

Well, heres the thing my car is running now, but two things were done to make it so... Like I said when I pulled my fuse 8, I lost about 1 amp in power through my chassis. So I finally decided to pull my radio and nothing ran through it, I am assuming it is a wire around the harness of the radio or the power to the radio... Not sure just happy that I have narrowed it down and my car start within a second of ignition.