Low charging voltage issues, please help!

Ok guys, haven't asked for much help here over the years, but I could really use some now. I've been having a charging voltage problem for the last couple years with my SVT and it has not been driven the majority of that time because of this issue. I am getting to the end of my patience with this problem and I am running out of things to try. I don't normally give up on things, but I am just about ready to give up on this car and move on. Here is the issue:

Alt went bad a couple years ago. Replaced with a off-brand reman that was nearly new out of a parts car. Could sometimes get it to charge at 14 if I wiggled the gray connector at the alternator, but pretty much stayed at 12v or so. Got a new gray connector from Ford and spliced it in so it fit snugly. Would sometimes charge at 13V+, but not for long. Inspected/cleaned mega fuse, all terminals, all grounds I could find. Wouldn't charge above 13V. Noticed the wiring from the pos to the engine bay fuse panel had cracked insulation. Replaced that with a new harness from Sam. No change in voltage. Did some more research and found that off-brand alternators can cause issues. Went and got a motorcraft reman alternator. No change in charging voltage. The battery tests out fine as well. Have not been able to get it to charge at more than 13V for quite some time now. Someone suggested the dimming lights mod for the alt. Should I try that? I don't want to hack up the harness if I don't have to. The only other option I have left is to take it to a friends shop to have him test it out. Almost every other shop won't touch it because it's "Modified" or they want to way over-charge me because of that. If I cut up the harness for the Dimming lights mod and it doesn't work, I'm afraid no one will touch it or they will point to that right away. Any other thoughts/advice?

How and where are you measuring the voltage?


Is it staying around 13 volts at least? I ask because my one car is just about always around 13.5 volts. The 14 volts is an ideal condition. I haven't had any issues and while it annoys me I haven't figured anything out. The voltage is as read from the volt gage I have tapped into the ignition switch yellow wire.


Do note that when a load is applied the voltage could drop down to less then 13 volts. I have completed the wiring mod but I can't say for certain that it made a difference.

I am measuring the voltage at the pos and negative cables at the battery. It has not been above 13 for months, but the car has been sitting because I haven't had a ton of time to work on it. Currently it charges at about 12.3 with only the DRL's on and that's it. I was happy when it was around 13.4 back around April, but that lasted about 2 days and then went right back to low charging again. Last night after installing the motorcraft alt and new mega fuse, it jumped to almost 13 when I turned the headlights on, but then stayed around 12.5 for a min and then began to drop slowly from the load without a charge. I've been trying to work through it with advice from other current and former CEG'rs. It appears as though the wiring mod is my last option here besides handing it to someone else and letting them figure it out

Frosty; try running a ground lead from the alternator directly to the battery. This will prove whether your ground circuit is good.

The fact that the reading goes up and down, suggests a poor/corroded connection somewhere ...G.

Well, I did the "dimming lights" mod and it didn't help. I called a shop to schedule a date to get it in because I don't have much time to work on it anymore these days with full time work and school. I forgot to try the ground lead. I understand wiring, but I'm not a pro. Where would you suggest attaching the ground lead to the battery and alternator? That's the last thing I can try. It's gotta be a voltage regulator wire issue or a ground issue. I just cant pinpoint it myself.