Anyone have a wiring diagram for the two GEM connectors that plug into the left side?

 

I guessing this is what you want.

 

Yes, thank you very much.
This will allow me to check for a problem in the circuitry. If nothing shows up then I am forced to the conclusion my GEM is bad.
I am chasing down a parasitic battery drain and have narrowed it down to larger plug on the side. When I pull that plug the battery drain drops to within acceptable levels.

 

Today I unplugged the larger gray plug from the GEM and tested each pin to see if there was a short to ground.
All checked out fine, including the #26 pin which is the ground circuit and had zero resistance to ground.

I guess the question now is, where can I get a quality GEM to replace this one with?
Or is it possible to repair the GEM?

 

Here's a good thread on rebuilding a GEM:

https://www.ford-trucks.com/forums/1...ater-leak.html

 

Boy that looks like a job!
Thanks for the link, I will give it a go once I have enough time.

 

Wow, how did I miss that thread... Subscribed and repped the author.

Jim, have you seen any water damage or evidence of corrosion on/around the GEM?

 

Actually I went ahead and tore into the GEM today.
Took a bit to get it dismantled as I was trying to be careful not to destroy anything.
Here's the bottom of layer:


I decided to take it one layer at a time so after dismantling I went ahead and cleaned up the plates with corrosion on them and reinstalled them.
The next layer wasn't as bad:


I suspect I will find more corrosion in the other layers. At this point what have I got to lose by trying to fix it?

 

Looks good, I'm in for the ride on this. So...is that sort of like a big computer chip? I can look at mechanical stuff and pretty much figure it out but that thing leaves me flabbergasted.

 

Next plate had corrosion:


Close up:




The next plate looked pretty good:


The problem here was more on the pins that protrude to the backside:


The next plate looked even better:


Again the problem was on the pins:


Cleaned everything with Electrical Contact Cleaner and red Scotchbrite pad for the most part. Used a brass brush and single edged razor blade for the heavier corrosion.

I found it fairly easy to reinstall the plates I removed under the hold down tabs by flexing the plate slightly in key locations.

Reassembled it and installed it in the truck. Started right up and I went for about a 3 mile test drive. When I got back I let it idle for a bit and then revved it up a couple of times. Engine sounded different for sure and seemed to rev up to 3k rpms much smoother than before.

Shut it off and disconnected the positive battery cables. Installed my VOM set to mA and checked battery drain - ugh still draining the battery at 170+ mA.

 

How long did you wait after reconnecting the batteries in series with the meter?

 

Do you mean when reading the VOM?
Until it stopped going up.

 

You should wait about 45 minutes before looking at it. It takes a while for the vehicle to finish doing all the things it needs to do after the batteries are connected.

 

Okay, I'll connect the batteries in the morning, drive it for a while and then park it for at least an hour before checking battery drain.

 

Added this thread to the 7.3L PSD Tech Folder