Hi all

The vehicle: 1993 F350 7.5Lv8 460

So I really wanted to replace the stock 75 amp alternator in my truck with a 130amp alternator. Lucky for me my 75amp alternator went out so I had an excuse to replace it.

Now I've looked into the options for this already. I've read the threads on junkyard harvesting alternators and harness's etc. I decided to get a new one and wire up my own harness. The first alternator I ordered from Rock Auto didn't fit which was frustrating enough to the point where I ended up going with this one:

https://www.jegs.com/i/Powermaster/713/57758/10002/-1

It is supposed to be a direct fit. Fair enough, it fits perfectly well mount wise.



I wired it right (as far as I know...it's not that complicated) and even put in a 150amp in line fuse



I started the truck up and we are running and starting great. Idles fine. Decided to take it to the local auto parts store for a battery and alternator test and here are the results



So...this is very frustrating especially considering the price and it's a "direct fit". I noticed on my way home the engine was at normal operating temperature and the battery gauge was going up slowly. It never went out of the "normal" range but was on the "L".

So I thought about swapping the resistor from my stock alternator into this one...and guess what...it doesn't fit!

So, my question is has anyone used this alternator before or does anyone have any advice for me about this?

thanks

 

Not saying you didnt, but with the rust you have, I would run a ground wire from Alt. case to engine block, per their instructions, just cause.

Alternator Ground: Many mounting brackets are powder/clear coated, painted, or plated. The alternator will not ground properly without a ground wire from the Alt. housing to the engine block. (This wire should match charge wire size) Battery must have a clean ground to engine block. Wire Connections: Be sure all terminals are crimped securely, and connections are clean and tight.
PowerPoint Presentation

1st post explains how to splice 1 wire into old harness
3G Alternator Install With Pictures - Ford Truck Enthusiasts Forums

 

I didn't ground from the back of the alternator as the OEM wasn't grounded in that fashion. But this is a good place to start. I appreciate the tip.

Same size as charging wire for the ground is surprising. I'm running 4 gauge for the charge. That's a fat grounding cable.

Anywhere to the block is fine?

 

I mean like...can I run a 4 gauge ground wire from the bolt of the pivot mount to the negative terminal on the battery? Or should I run a 4 gauge wire from the back of the alternator to the negative terminal on the battery or is the block better?

 

I would think #6 or #8 will be fine, I found how to splice into old harness with one wire, and added to above post I made, Sorry, for the back and forth.

 

Oh yeah....pretty sure I found the issue in a big way.

​​​​here is the ground connection from the battery to the block



Beautiful right?

Anyhow, I cannot get to this thing. It's really difficult to access and I'm not sure sanding all that down is worth it anyways. I'm thinking of just cutting it and grounding it somewhere else. I just wanted to check with yall here and see if anyone has a suggestion as to where I should mount it?

I was thinking on this bolt here:


Thoughts?

Thanks

 

Also I have a follow up newb question

There is a smaller wire that's also connected to the block that appears to run to the chassis. That's correct right? The battery is grounded to the block and the chassis?

So the smaller wire I can run from the battery to anywhere on the frame?

 

we have numerous grounds, on our trucks, I would clean as many as I could find---Ground Points - Ford Truck Enthusiasts Forums
spot in pic will be better than the other, (prolly break stud off trying to remove/clean)

 

So I've done a lot and I'm freaking NOWHERE. I disassembled the main ground to the block. Sanded everything down to the BARE METAL. Same with the ground from the battery to the body and from the block to the frame. And I ran a ground from the alternator mount to the battery with a 4 gauge wire.

The battery light is now on when the truck is running.

Tested the alternator. Still 12.3 volts at idle.

I put a BRAND NEW battery in. 12.3 volts at idle.

I figured maybe the original wiring harness (3 pin connector) that I reused was bad maybe. So I bought a new one. Still 12.3 volts at idle.

To sum up: brand new alternator, brand new harness, brand new battery, all grounds have been thoroughly sanded to bare metal and I used new terminal connections, and I've ran a ground from the alternator to the battery.

I'm nowhere. I test drive the truck and then check the battery and sure enough it's getting drained and the battery light is on.

What am I missing here?

The only thing I figure is the alternator was bad from the factory.

Thoughts?

 

Tried connection alternator directly to battery to see if it made a difference. None what so ever. Thinking alternator is defective unless someone has a better idea.

 

Did you splice the 1 wire into the old harness, if you did, check that it has 12vdc, with key in on position, if it has 12vdc,, alternator may be bad. (see below) 2 different quotes.

"(Now onto the wiring. Do not let it intimidate you. You have 3 wires, "A,S, and I" coming out of the voltage regulator. Starting with "A" (the yellow wire), it only needs an eyelet on it and then loop it to the battery post of the alternator. Next wire is "S" (the white wire). It comes out of the connector and the other end plugs into the remaining terminal of the alternator. *This is already done by the factory as can be seen when you take the plastic wiring loom off the harness.* Last wire is the "I" (the green with red stripe wire). You will need to cut the green with red stripe wire in the truck's alternator wiring harness. You then solder this wire to the same color one in the truck's harness. One of the most confusing parts of the mod is now done.")

("You need to connect the single wire left on the harness to a wire that is HOT with the key in RUN. Ford has used a Green/Red wire on their vehicles for over 50 years. So it’s simple to find that wire that went to the old alternator and use it now.")

 

I dont understand what this guy is talking about in that thread. The green wire is the ignition wire. I connected it to the ignition like the original alternator was. What needs to be soldered? That doesnt make any sense to me. If I had the ignition wire connected incorrectly I would have starting problems wouldn't i? Truck starts and runs just fine. I'm just not getting anything about 12.3 volts when running

 

I'm a little late to the party here but maybe these diagrams will help. these are for a 91 f150 w/ the 4.9L. No sure how different they will be from yours.

I had the same exact problem a while back and I ended up finding a broken wire in the 3 pin connector. A small splice and some heat shrink and I was back in action... can't remember which wire it was though.

 

So when I put the positive test lead on the "S" terminal of the regulator plug and the negative lead on the battery ground I'm getting around 12v with the ignition off and 0v with the ignition on.

 

Here is how I did the green ignition wire


Factory plug for the ignition. I reused it.


Then I spliced it into the 3 pin wiring harness of the alternator