Alternator Harness

Jamie V

Jamie V

Well-known member
Does anyone know where I can buy a replacement factory Alternator harness? I’m sure it’s not specific to a Lightning.

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I’m building a new harness with a heavier gauge wire and I don’t want to cut up/modify this one from my 4,800 mile original truck.

I am hoping to find one that’s new or from a lower mileage garaged truck so the wires & plugs are in good shape and not real brittle.
 
Jamie,

Have you contacted Ed?

He might honestly have one or two new ones he’s produced or maybe he’ll make one for you.
 
Ron, I’m not sure if Ed’s kits have all the plugs on them to plug into the Alt (probably do) or if it has the plug to go into the under hood harness (for the battery light in the dash).
 
Jamie V said:
Ron, I’m not sure if Ed’s kits have all the plugs on them to plug into the Alt (probably do) or if it has the plug to go into the under hood harness (for the battery light in the dash).
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Jamie, it does use all the factory hook ups. You have to cut one factory plug and reattach it. May be the one for the battery light. I have some pics but for some reason cannot post from my iPad. I can email/ text if you want.
 
QUIKSVT said:
You have to cut one factory plug and reattach it. May be the one for the battery light. I have some pics but for some reason cannot post from my iPad. I can email/ text if you want.
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I don’t want to cut my factory harness at all. If you want to email me the picture that would be great. jfastford@comcast.net


Steve83 said:
Unless you're running a ridiculously-high-output alternator, the original is fine. It's built to handle the 130A 3G, which commonly puts out >150A. But this harness is PnP, and can obviously handle >175A:

(phone app link)
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I have a 130amp alternator now but it’s not enough so I’m going to a 200amp unit. What year expedition is that wiring harness from? Do you have a factory part number for it?
 
Have you checked voltage at the battery and on the alternator stud to see the voltage drop? Checked at idle and at like 3,000 rpms?
 
Jamie V said:
Have you checked voltage at the battery and on the alternator stud to see the voltage drop? Checked at idle and at like 3,000 rpms?
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Checked it with a VOM at idle with both fans running and the head lights on. My Holley dash has a volt meter on it that I can see when driving, and voltage is data logged also. I had an Explorer 3G on the Lightning that worked fine, I only went with the Powermaster becuase the bearing failed in the 3G.

I doubt you'll ever pull enough amps for the stock harness to be a problem. I tested the charging system in my F350 by turning EVERYTHING,including dual engine and trans cooler fans,on and letting it idle in 90 degree heat for an hour. Amp clamp read 150 amp draw at the alt cable. No problems. Every summer I drive it 10-15 miles off the pavement on the beach for vacation. Wanted to know it could handle it.
 
What he's say is that, even with a million-amp alternator, it will only put out what the truck needs. And if you're not using 175A, the stock or Expedition harness will be fine. You'd have to add some heavy engine-running loads (like a big power inverter for a chest-freezer in the bed) AND a really-high-output alt before you'd tax the stock charge wire.

I don't have a PN for the Ex harness, but they're common in JYs.
 
I upgraded to a 130amp alternator and it still can’t keep up. With everything on I’m drawing about 120amps and the voltage is down to 12.40v at the battery but 12.75v on the back of the alternator.
 
12.75 v at idle? You prob need to speed the alt up with a smaller pulley. I ran a small pulley on my 3G and voltage at idle stayed above 13.xx, don't remember the exact numbers.
 
Brian with your 150amp draw that you tested what was the voltage at the battery and at the back of the alternator?

If I’m seeing .35v drop at 120amps through the same stock wiring as your running you should be more at 150amp draw.
 
Jamie V said:
Brian with your 150amp draw that you tested what was the voltage at the battery and at the back of the alternator?
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I did that test on my F350 about 10yrs ago, so I don't remember the voltage #s, just that it was good.

Jamie V said:
If I’m seeing .35v drop at 120amps through the same stock wiring as your running you should be more at 150amp draw.
Click to expand...

Are you really pulling 120 amps?
 
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