High output alternator

[DallasTahoe]

Upgrade all grounds coming from the battery, grounds especially with larger gauge wire than stock, and power cable from alternator to battery and add a ground from alternator case using the alternator mount to the battery ground. Chassis to frame, motor to frame, frame to battery


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[Joe Dirte]

How are you testing the output voltage? Check with a multimeter from the positive of the alternator to the alternator case. You may have some gnarly voltage drop from the alternator to the gauge in the dash. If that's the case, then you'll need to upgrade your wiring from engine and body ground to battery negative, and power wire from alternator and power distribution box to positive battery. If you're still low, connect a wire from the sending connector in the pigtail to the distribution box feed. You can check coverage drop across each wire but if you're going to do the big three anyway, that should take out the voltage drop... well mostly anyway, there's always going to be a slight voltage drop across any wire.

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I swapped old factory alt in and she's reading 14 in gauges. It ain't running worth a damn now so not overly concerned with it at this point.

 

[Ken K]

Yes the 96-98 classics are a direct bolt on, plug may be different. The 88-95 have a different alternator and dont know the number off the top of my head. Its smaller and has a threaded mounting hole on the back side of the alternator. The aluminum bracket has 3 "ears" for the 88-95 compared to the 4 "ears" of the 96-98. You can see the bracket in my build thread.

Maybe I am not too good about figuring out how to find things, but how do I find the Alternator bracket build link/thread? Ken k.

 

[kennythewelder]

My big 3 is this. 1positive cable from the alt to the battery with a 150 amp fuse. 1 negitive wire from the alt case back to the battery ground. 1 neg wire from bat ground to frame. 1 neg from bat to engine block. 1 neg from bat to truck cab. All of mine is AWG #2 welding lead. It is common to use 1/0 wire for this up grade. 1/0 wire is larger than AWG #2 wire. My amp is only 680 watt. I have the 4 high mod, and both high and low beams are relayed to the battery. I also have 2 electric fans for my radiator. I did away with the old mechanical cooling fan. Oh and you do not remove any of the OE wiring. You just add to whats there all ready. I TIG welded 2 3/8 bolts back to back to give me enough room for all of the extra ground leads.

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[RawbDidIt]

My big 3 is this. 1positive cable from the alt to the battery with a 150 amp fuse. 1 negitive wire from the alt case back to the battery ground. 1 neg wire from bat ground to frame. 1 neg from bat to engine block. 1 neg from bat to truck cab. All of mine is AWG #2 welding lead. It is common to use 1/0 wire for this up grade. 1/0 wire is larger than AWG #2 wire. My amp is only 680 watt. I have the 4 high mod, and both high and low beams are relayed to the battery. I also have 2 electric fans for my radiator. I did away with the old mechanical cooling fan. Oh and you do not remove any of the OE wiring. You just add to whats there all ready. I TIG welded 2 3/8 bolts back to back to give me enough room for all of the extra ground leads.

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Question: I've always wondered this. If my alternator can put out 222A what do I fuse it for? Theoretically after my 2 amps, light bar, and other assorted accessories I have total potential draw at around 200A (yes, I know I need a second battery, but this is also based on fuse requirements for the added accessories, meaning there's quite a bit of headroom already built in to the calculation, I also don't plan on maxing out my sound system with all of my lights and other accessories on) should I fuse for 250A?

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[kennythewelder]

Yes, I would do 250 amp. where issues come in, is when the alt sticks in wide open charge rate, or if there is a short. I had my OE do that. The OE wiring got so hot, that it melted an aluminum cooling pipe that it was laying on, before the fuseible link burnt. Thats what the fuse is for. You dont want a short to fry and catch the whole truck on fire. You want a little over max out put for the fuse rating. If not them the fuse will get hot at max draw and burn out in time.

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[DallasTahoe]

Yes, I would do 250 amp. where issues come in, is when the alt sticks in wide open charge rate, or if there is a short. I had my OE do that. The OE wiring got so hot, that it melted an aluminum cooling pipe that it was laying on, before the fuseible link burnt. Thats what the fuse is for. You dont want a short to fry and catch the whole truck on fire. You want a little over max out put for the fuse rating. If not them the fuse will get hot at max draw and burn out in time.

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No I wouldn’t do 250, that’s wayyy too much especially considering if your alternator did fail do you really want it to be able to pump 250 amps through your electrical system that wasn’t meant for that kind of power?? Do yourself a favor and use at maximum a 175amp mega fuse that’s what came from the factory, otherwise you run the risk of burning your rig down should something go wrong, besides if you have everything on there is almost no way your using 250amps


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[DallasTahoe]

I’m running two batteries, a 140amp alternator, 3sets of auxiliary lights, a big amp and auxiliary fans, all through a solenoid and fuses and I never reach even close to 200 amps if everything in the truck is on


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[Cokeman95]

Kenny where did you purchase your fusible link from?

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[kennythewelder]

Kenny where did you purchase your fusible link from?

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I found one at the salvage yard. As for the 250 amp fuse, I asked the custom shop where I bought my fuse about the size I needed. They said for 1/0 wire they use a 250. Just passing along what I was told, be it rite or wrong.