Hello, I have a 01 f250 7.3L. Over the holiday weekend I attacked a miss I am having. Changed out the UVCH, valve covers, and glow plugs. Upgraded the glow plug relay to a white rogers relay. While I had it torn apart, I took the wiring harness off that powers glow plugs, aih, ect ect. I carefully took all the wire loom of to replace it with new loom. Doing small portions at a time to ensure I didn’t mix any wires, it fit the same going in as it did coming out. Factory loom was falling apart. While I had the loom off I inspected all the wires for any chaffing. No chaffing at all. Now that I have it all back together, the alternator isn’t charging. I’ve double and triple checked that everything is wired up how it was when I took it apart. I’ve cleaned all ground connections, and replaced all the battery cables except for ground cables. I’ve replaced the alternator with a new one, that tests out good on the bench tester at the parts store. Batteries test out good as well. I can get the truck to start by charging the batteries, but I’m seeing a discharge on the meter at the batteries. As if the alternator were bad. I’ve checked #6 fuse under the hood, good. I’ve checked #29 fuse in the cab, good. If I run a jumper wire back to the solenoid from the output post, my issue remains. If I hook the jumper cable from the output post to the pos terminal it starts charging. Also the connector to the alternator has power on each lug. Green wire with red stripe and orange wire with blue stripe both test good.

I can’t figure this out to save my life. What am I missing? The starter relay is new as well.

 

Wiggle the alternator pigtail to see if makes the alternator start charging.

 

I figured it out. I appreciate your response though! I had the wiring harness hooked up to the wrong lug on the starter solenoid. I’m not sure how I over looked that (face palm). A day wasted over a silly error on my part.

 

For future reference, the first photo is the correct way to wire the starter solenoid. The second picture is the wrong way.

So, if you find yourself with a charging issue after messing with the harness, check the solenoid and be sure it’s wired correctly. Or it won’t charge. Your wallet will thank you, trust me lol!

Correct way

Wrong way

 

That looks like a pretty small wire you have feeding that solenoid. Do my eyes deceive me?

 

The small (red) wire is the signal wire for the starter. The feed wire is on the bottom in the picture, black with a copper lug soldered on. I used 32mm 600v welding cable for all the main feeds and to connect the batteries.

 

OK...so...does the starter get fed from the battery and the solenoid there only clicks the solenoid? For some reason, I'm thinking that the starter wire feeds through that solenoid on mine and has a main battery feed to and from.

 

The OEM wire is pretty small - looks different when part of the factory harness.

 

Mine is wired with 3 feeds coming off the passenger side battery. One of those feeds connects to the positive post on the driver side battery. the second feed goes to the starter, and the third goes to the starter solenoid. Which powers the harness for the motor, and the harness for the truck. The little red wire just sends the signal from the starter solenoid to the solenoid on the starter. The wire I use for that is actually a tiny bit bigger than the stock wire.

 

Ah yes. That would do it. Those double gray wires are fusible links by the way.

This picture that Jeff posted shows the factory terminal that does a good job of hiding which wire goes where. The bigger wire is the supply from the PS battery going to the lower always-hot terminal (as you found out) of the starter solenoid. The small wire goes is the signal wire to the solenoid on the starter itself (as you also found out).

Finally you can be a smartass like me and install a heavy-duty Trombetta relay which has to be rotated 90º to mount because the lugs are different and really confuse things.

 

[QUOTE=FordTruckNoob;20173853]Ah yes. That would do it. Those double gray wires are fusible links by the way.

I was positive that the harnesses didn’t go together on that solenoid. After staring at it for 3-4 days, it made sense (in my mind) that the harness for the GP (I’m unsure of the actual names of the two harnesses) should only activate when the key was on. It didn’t make any sense for that harness to be connected to a always hot terminal. Because the glow plugs would stay on all the time. And the only function that wasn’t working was the alternator… it wasn’t until I realized the GP are on their own relay. Insult to injury… I even replaced/upgraded the GP relay. A real “Ha ha, you *******” moment. I had myself convinced that I messed up the output wire for the alternator somehow, by messing with that harness. I almost ran a dedicated cable from the alt to the pos post on one the batteries just until I could get back into the harness and replace the wire. The only thing that stopped me was 1, I didn’t know if that was safe for our trucks. Second, it still wasn’t charging when I ran a jumper wire from the output post back to the solenoid. Needless to say, 1+1 didn’t equal 2.

im just glad it turned out to be a bone head mistake on my part. And a simple one at that… it just took an extra set of eyes from a friend to identify the issue.

 

[QUOTE=7.3powerstrokeBob;20173984]
Unfortunately we are all guilty of bonehead mistakes! Glad you got yours sorted without throwing too much money/parts at it!