Alternator Swap Out

javelinadave

Administrator
Staff member
It goes around the engine as to avoid the exhaust manifold, turbocharger and everything else that is hot.
 

Viton

Well-known member
It goes around the engine as to avoid the exhaust manifold, turbocharger and everything else that is hot.

Well then, the length & subsequent voltage loss is the main determining factor in a DC system. Seems the shortest length shown in the various charts is 10'. Most show 4, or 6 gauge wire, and that would be assuming that your loads would pull the full 100 Amps, which you probably won't pull.
Do you have big Amp loads in mind ?

Remember, too thin of a wire and it ends up acting like a fuse, heating up & burning through.
Which brings to mind another aspect of wire size, the operating temperature, a component of Ampacity.
Hotter wires reduce the flow of electrons which requires a larger gauge size to keep the flow up without over heating.
Think I'd opt for a single strand of #4.

Also, wondering if you'll find an inline diode on the factory wire just outside the existing alternator?
 

Uncle Douglas

Well-known member
Callsign: delete
I just received my 300Tdi 100 amp alternator from Robert Davis (thank you sir!) and plan on installing it this week. How much of a wiring upgrade have you done gauge wise for those who have installed an upgraded unit?

https://nas-row.com/showthread.php?t=419

I replaced a 65 with a 100 and made no upgrades. Ran like that for many years. Pretty sure I never came close to needing the amperage except when winching.The on a 300 tdi 130 with minimal electric draw, ie no off road lights etc. The only reason I made the swap was the bearing in the original was grinding.
 

jymmiejamz

Founding Member
Callsign: KN4JHI
I replaced a 65 with a 100 and made no upgrades. Ran like that for many years. Pretty sure I never came close to needing the amperage except when winching.The on a 300 tdi 130 with minimal electric draw, ie no off road lights etc. The only reason I made the swap was the bearing in the original was grinding.

I put a Discovery 120A (I think) alternator on my 110 and did not upgrade the wiring. I also put a much bigger alternator on my MGB without upgrading the wiring. Sure, its not the right way to do it, but it worked fine.
 

DefendersNW

Well-known member
Dave,

No need to do anything - if you want to help the system out a bit, run a second wire in parallel from the alternator to the hot lug on the starter. DC doesn't care if the wire strands are sheathed together or not, and redundancy is a good thing anyway. Each wire is capable of carrying the full load so a failure on either one isn't going to stop the truck.

We always stock 100amp alternators and I've added them to all of my trucks when the 65a stock unit goes out.
 
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