Upgrading alternator, upgrade wiring?

[derekjl]

Thinking of upgrading to a higher output alternator. I purchased and installed an AC Delco alternator about one year ago and I believe I got a dud. It's very loud, voltage drops when all of the accessories are on, etc. It works, but just not as well as the one it replaced. I'm thinking of going with the Powermaster 140 amp unit. Should the wiring to the battery also be upgraded? What about the ground? Thanks ahead of time.

 

[Doubeleive]

some people do what's called the "big 3" upgrade, especially if you run any amplifiers or other equipment, it's basically 3 pieces of 0 gauge wire that are added on. one would go from the alternator mounting bracket to the battery ground post, one would go from the battery ground to the frame, and the third from the alternator output to the positive on the battery.
but if you are getting power drops like dimming lights and gauges it's likely because of a weak battery, if the alternator was bad the battery would just die period

 

[derekjl]

some people do what's called the "big 3" upgrade, especially if you run any amplifiers or other equipment, it's basically 3 pieces of 0 gauge wire that are added on. one would go from the alternator mounting bracket to the battery ground post, one would go from the battery ground to the frame, and the third from the alternator output to the positive on the battery.
but if you are getting power drops like dimming lights and gauges it's likely because of a weak battery, if the alternator was bad the battery would just die period

I’m positive it is the alternator. I’ve replaced the battery with a much better one with higher CCAs and the issue remains. It didn’t do this with that previous alternator, but that one died. I figured the AC Delco new version was the best bet. First thing I noticed was the voltage gauge fluctuation with the turn signal. Like it said, it is also very loud and whines. When everything in the truck is on (fan, wipers, rear defrost, etc.) and I’m in drive at a stoplight, the voltage goes way down and headlights dim, everything slows down until I step on the gas again. Here is a video I made last year...this sound gets annoying in stop and go traffic. Just to reiterate, the alternator isn't necessarily "bad", it is just barely adequate unless any power draw is off. I chalk it up to being a Chinese-made POS...like most car parts today lol.

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[Wylie_Tahoe]

A higher output alternator, does need to have a supply cable thats capable of handling its amperage. So I would inspect the existing cable and see what gauge it is. DO some math (or google cheater chart for current capacity) and see if you need to upgrade the cable, for the future alt.

Does it hurt to upgrade the cable? no. Is there a small advantage to going to a larger ga then needed, but no benefit to overkill.

The alternator ground direct to the block, through its housing, so no ground cable upgrade needed with an alternator upgrade.

With that said, I would inspect and test all the main cables to make sure your new symptoms with this alternator, are not cause by an external issue. A low producing alternator can be seen with basic test equipment.

 

[iamdub]

Factory wiring is marginally sufficient at best and that's when it's new. You have wiring and connections that have been subjected to ~20 years of temperature changes, moisture, movement, etc.

I'd absolutely upgrade the wiring. I'd run 0 gauge from the alternator positive to the battery, from the battery negative to the frame and from the engine block to the frame. The alternator is already grounded to the engine block through it's body so no need to ground it directly to the battery negative. It's easier, cleaner and shorter to go from the engine block to the frame. Honestly, I'd bet that you'd see an improvement just doing this while still running your current alternator. If it were me, I'd do the Big 3 before changing the alternator just to see, then replace the alternator. The strength of an alternator doesn't mean shit if it's connected to a weak and insufficient circuit.

To give you an idea of how the factory wiring is marginal if not undersized, I've see drastic improvements in headlight output by just replacing the stock headlight wiring with 10 gauge, which is the largest wire that can be squeezed into the pins of the relay box. I'd just use a relay circuit fed from the battery and triggered by the headlight circuit than replace the actual factory headlight wiring in the harness, though.

 

[Wylie_Tahoe]

Nothing against a little over engineering, but 1/0 alt supply would be right for a 400 amp alternator! Hell, thats a gas powered generator at that point