I just ordered a replacement alternator "Pure Power" from Tusconalternator.com . This is a 240A alternator and the web site recommended an upgraded wire kit. Long story short they recommend running an additional + cable from the alternator to the positive battery terminal while leaving the existing cable to the alt fuse in place. What do you guys think of this idea? I don't think I'll ever be pushing anything close to 240A, I was really just looking for a bit more output than stock at idle. The only significant additional electrical load I have at the moment is the connection to my truck camper which typically pulls 10-20A and is fused at 50A.

What are the odds that if I leave my existing cabling in place (other than checking/cleaning my grounds) that I will end up popping the 140A alternator fuse? Worst case seems to be if I were to run down my truck batteries while parked and then jump start the truck in which case it might charge the truck batteries at a pretty high current for a bit but I still doubt it would be 140A. What do you guys think?

1 hour ago, RayNAz said:

What are the odds that if I leave my existing cabling in place (other than checking/cleaning my grounds) that I will end up popping the 140A alternator fuse? Worst case seems to be if I were to run down my truck batteries while parked and then jump start the truck in which case it might charge the truck batteries at a pretty high current for a bit but I still doubt it would be 140A. What do you guys think?

The 140 amp fuse is not there to protect the alternator. It is there for safety reasons in case the alternator or alternator output wiring shorted directly to ground. A fire could easily be started from the large amount of stored energy available from two large batteries that would have a direct path to ground if the alternator output circuit was not fused. By adding a non-fused second output wire, you are contributing to the potential for a fire.

Personally, I would remove the old alternator output wire to the 140 amp fuse. I would run a single wire of the correct diameter through a suitable 250 amp fuse to the passenger side battery. The W-T Ground Reference mod wires the alternator output to the passenger side battery as part of the rewiring procedure.

• John

3 hours ago, Tractorman said:

Personally, I would remove the old alternator output wire to the 140 amp fuse. I would run a single wire of the correct diameter through a suitable 250 amp fuse to the passenger side battery. The W-T Ground Reference mod wires the alternator output to the passenger side battery as part of the rewiring procedure.

• John

Yeah, the un-fused connection running all the way across the engine bay to a battery sounded like a bad idea to me for that exact reason. That's why I was considering leaving the existing fused cable in place as-is and skipping the upgraded cable. If I go with your approach, do you have a suggestion for a suitable fuse type and holder?

The photo below shows a 250 amp fuse and fuse holder similar to the style of fuse that I used. My fuse is 150 amp and has been reliable for over 3 years and over 30,000 miles.

• John

I second what @Tractorman recommends. last October, while on a trip to the Portland area, my alternator shorted to ground. The short blew the 150-amp fuse, similar to the photo above. I had installed it after doing the "W-T" modification. With out that fuse and the properly gauged wire there could have been a catastrophic fire under the hood.

3 hours ago, Tractorman said:

The photo below shows a 250 amp fuse and fuse holder similar to the style of fuse that I used. My fuse is 150 amp and has been reliable for over 3 years and over 30,000 miles.

Thanks!