New Alternator
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New User
Joined: Apr 2017
Posts: 2
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New Alternator
Hello Everyone,
Recently my battery has been dying and I have determined it to be the alternator. The current alternator OEM and so it is a 3 wire setup. Truck is a 1977 F150 with a 351M. I have done my research but still have a few questions. My questions are:
1. Does anyone make a 3 wire alternator compatible with the 351M?
2. I found plenty of alternators claiming to be 1 or 3 wire, how does this work?
3. Will this require getting a new voltage regulator?
4. Can I run a larger gauge wire between the alternator and the battery to assist the OEM wiring harness for the higher amps?
Any help would be greatly appreciated, thanks.
-Seth
Recently my battery has been dying and I have determined it to be the alternator. The current alternator OEM and so it is a 3 wire setup. Truck is a 1977 F150 with a 351M. I have done my research but still have a few questions. My questions are:
1. Does anyone make a 3 wire alternator compatible with the 351M?
2. I found plenty of alternators claiming to be 1 or 3 wire, how does this work?
3. Will this require getting a new voltage regulator?
4. Can I run a larger gauge wire between the alternator and the battery to assist the OEM wiring harness for the higher amps?
Any help would be greatly appreciated, thanks.
-Seth
Tuned
Joined: Feb 2002
Posts: 441
Likes: 0
From: Vicksburg, MS
Have you read about the 130amp retrofit?
https://www.ford-trucks.com/forums/1...l#post14955940
I plan to get a salvaged alternator soon and do the swap.
https://www.ford-trucks.com/forums/1...l#post14955940
I plan to get a salvaged alternator soon and do the swap.
Fleet Owner
Joined: Dec 2009
Posts: 20,678
Likes: 82
From: NorCal
MOFW = Men of Few Words
1.Yes
2. A "one wire" eliminates the wiring associated with an external voltage regulator.
3. No, since it is internally regulated. But if the internal regulator is bad, then yes, it would require replacement.
4. Yes.
2. A "one wire" eliminates the wiring associated with an external voltage regulator.
3. No, since it is internally regulated. But if the internal regulator is bad, then yes, it would require replacement.
4. Yes.
Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
A 1 wire unit doesn't totally rid the truck of the voltage regulator wiring unless you want to do a lot of splicing. You still leave it connected with the setup. It's as simple as it gets though...run one wire to ground and the other to the hot side of the battery.
Summit Racing sells a Tuff Stuff 1 wire alternator that's a direct bolt in for under $100. Now that said, I bought one and it's crapped out on me after 2 months. Hoping that's a fluke, and Summit is in the process of overnighting me a new one.
Summit Racing sells a Tuff Stuff 1 wire alternator that's a direct bolt in for under $100. Now that said, I bought one and it's crapped out on me after 2 months. Hoping that's a fluke, and Summit is in the process of overnighting me a new one.
More Turbo
Joined: Jun 2015
Posts: 534
Likes: 27
From: North Texas
I got a NEW 3 wire from Summit (Powermaster 7078) and it's been working like a champ. 80amp's so its 25-50% more juice than OEM and wires into existing setup (External regulator is still required, I'd replace at the same time). Coming up on 2 years, no issues.
https://www.summitracing.com/parts/pwm-7078
https://www.summitracing.com/parts/pwm-7078
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
On question 4 "can I run a heavier gauge wire". Yes and a little more detail. I think it is a really good idea to increase wire size when increasing amps. The OE harness was made for a pretty small alternator and is light gauge.
If you go single wire, the heavier charge wire is important since there is no remote regulator to compensate for voltage drop in the charge wire
A heavy wire from the alternator to the fender relay will do it. I would suggest at least 8 gauge. 6 gauge would be better. A heavy duty fuse rated at least 25% higher than the alternator or a fusible link 2 gauge sizes lighter than the charge wire would provide protection from shorts.
With the added wire, the alternator (if equipped) will not function. It doesn't work very well anyhow so no loss. Adding a volt meter to a switched circuit will tell you what is going on with the system.
If you go single wire, the heavier charge wire is important since there is no remote regulator to compensate for voltage drop in the charge wire
A heavy wire from the alternator to the fender relay will do it. I would suggest at least 8 gauge. 6 gauge would be better. A heavy duty fuse rated at least 25% higher than the alternator or a fusible link 2 gauge sizes lighter than the charge wire would provide protection from shorts.
With the added wire, the alternator (if equipped) will not function. It doesn't work very well anyhow so no loss. Adding a volt meter to a switched circuit will tell you what is going on with the system.
Laughing Gas
Joined: Mar 2015
Posts: 885
Likes: 2
From: Pittsburgh
I replaced my 3-wire in my 79 351m a couple of months ago. Got it at AutoZone, went on without issue. I bought a 70-75amp (can't remember exactly) to replace the factory 65amp.
While the 130amp upgrade seems like a great idea, I was already deep into a different project and didn't want to be messing around with something else. Plus I haven't and don't plan to add anything that really would need a power upgrade that big.
While the 130amp upgrade seems like a great idea, I was already deep into a different project and didn't want to be messing around with something else. Plus I haven't and don't plan to add anything that really would need a power upgrade that big.
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New User
Joined: Apr 2017
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Thanks for the replies everyone, I will look into the 130 amp upgrade and see if it looks reasonable given my time restraints. Otherwise, one of the alt's described above will do.
My second question was pertaining to whether a 1 or 3 wire alternator comes with the necessary hardware such as the extra connection posts? In all the pictures there is nothing other than the one battery connection shown.
My second question was pertaining to whether a 1 or 3 wire alternator comes with the necessary hardware such as the extra connection posts? In all the pictures there is nothing other than the one battery connection shown.
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Elder User
Joined: Oct 2016
Posts: 712
Likes: 1
From: Mesa, AZ
The 1 wire alternator requires a heavy guage wire to go to the battery. You can buy one or you can make one. It also suggests at least a 10 guage ground wire. The connection points are on the alternator...a nut holds the hot wire on and a screw typically holds the ground wire. I ran my ground wire just below the alternator and used the same ground bolt that the negative battery cable grounds to on the engine head.
Fleet Mechanic
Joined: Aug 2004
Posts: 1,311
Likes: 31
From: Nevada
Tuff Stuff
I put in a 3 wire tuff stuff from Summit and its been flawless, good reviews on that brand, reasonably priced and Summit has a warehouse in my State so its here the next day..... just my 2 cents.... 
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