OEM 80A Fuse on pre-2000 V6 Tacoma used with 2000 & later 80A Alternator

Merry Christmas and Happy Holidays guys and gals!
This is just a head-up for the early pre-2000 V6 Taco owners like me. AFAIK and as a general guideline: It appears the factory put a 60A alternator in the '95-'96 V6 Taco, a 70A in the '97-'99 V6 Taco, and an 80A in the 2000 and later V6 Taco. I replaced the original 60A or 70A Denso alternator on my 01/97 built '97 V6 Taco 4x4 with a new aftermarket Nippondenso 80A alternator. The problem I see is the 80A fuse in the fuse box. An 80A fuse on my now 80A alternator circuit amounts to a fuse test IMO. The 2000 and later V6 Tacoma appears to have a 120A fuse using the same general type 80A alternator as I have installed now. I think it wise to change my early-Taco 80A fuse to the later-Taco 120A fuse to keep the 80A alternator changing while running the Warn winch on front of my '97 Taco under heavy load. The OEM wiring from alternator/fuse box/battery appears to be 10ga., so should be adequate to carry the extra 10-20A the new 80A alternator is capable of delivering. All you guys who upgraded to the

$163 Denso 210-0461 Denso First Time Fit Alternator - 210-0461

Denso 210-0461 105A alternator in your pre-2000 V6 Tacoma may also want to consider changing out your 80A fuse if you have not already done so. This very-useful information was previously posted by chagovatoloco, but was a bit buried on page 7: 1st gen 105 amp bolt in alternator. | Page 7 | Tacoma World. .02

EDIT: If any of our resident electrical engineers see a flaw in my limited-electrical-knowledge reasoning above, please correct me.

 

It really only protects the wiring harness if the over all system load exceeds 80 amps.
The lower the fuse the more protection.

 

You would typically try to size your system so the max current doesn't exceed 80% of the system's capability, you always want some overhead. Theoretically the system will handle 100% providing there were no flaws or aging of any of the system's components. With age and manufacturing variances that's not as likely and the downside to that kind of failure might not be the fuse, could be an expensive alternator or damaged wiring. In the electrical power industry components were sized 20~30% higher capacity then the largest expected load. Obviously the winch throws a wrench into that but you don't want to demand 100% out of your system, ideally you'd size it at least 20% larger then you need.

 

Understood and I appreciate the input. The cost of replacing the alternator and wiring is very much secondary. It would actually be a good idea to upgrade to the

$163 Denso 210-0461 Denso First Time Fit Alternator - 210-0461

Denso 210-0461 105A alternator now that they are once again available. Losing the ability to charge the battery while being required to run the winch hard over extended periods is my main concern. When conditions warrant it such as when doing rescue-recovery after a hurricane/tornado, I carry a spare AGM battery in the Taco as back-up power. Getting REALLY stuck way back in the woods where there is no assistance available nearly cost me this '97 Taco on one occasion due to fast rising Mississippi River flood waters. And the Taco has already been required to do some very hard pulls with the 80A Denso alternator sending its current thru the OEM 80A fuse. I was probably right at the limit of blowing the OEM 80A fuse without a spare for that fuse. Using a snatch block as a doubler on the winch line probably kept the current load on the 80A fuse slightly below max allowable. My thinking is to replace the OEM 80A fuse with the later Taco 120A fuse now and carry at least 1 spare fuse. The Taco charging system wiring and ground wiring will also get upgraded to heavier gauge copper battery cable, probably the tinned marine grade cable since that is what I routinely used on yacht mtx. Just a shame that I don't have any copper welding cable scraps left over from my years as an iron worker.

 

Your looking at this wrong .
All the electric inthe system is pulled out of the battery.

The alternator just keeps the battery up to where it needs to be.

I winched with my 80 Amp alternator just fine .

Though not having a sound system on wheels helped.

The output of the alternator just determines the length of recovery time for the battery

 

Fuse for the wire...

One common misconception about choosing the correct fuse size is that it’s dependent on the load of the circuit. Actually, the load of the circuit should have nothing to do with choosing a fuse size. The fuse size should be based on the SMALLEST wire (largest gage number) in the circuit.



Take the maximum current value obtained from the table and find the largest fuse you can find that still falls within the limitations. DO NOT EXCEED THE VALUES ON THIS TABLE. Common automotive blade-style fuses exist at 5A-20A in 5A Increments. Ex: 5A,10A,15A,20A

 

Yes, I understand that the winch is drawing its current from the battery. But given the perfect world where the alternator is putting out its full rated 80A of current and the fuse is a spot-on 80A fuse, the 80A fuse should be right on the very edge of burning thru when the 80A alternator is delivering its full rated current capacity to the depleted battery thru the 80A fuse during and after running the winch under full load. In our imperfect world, the 80A alternator may be capable of delivering slightly more than 80A of current, the 80A fuse may blow at a slightly lesser value, so the fuse should burn to protect the downstream wiring. I was taught that a fuse has to be at least equal to the current you intend to run thru it, but normally 10-15% above that. And yes, the wiring is also part of the equation. But the smallest wiring in the charging circuit is the short 10ga wiring from the alternator to the fuse box to the battery. On that short a span, it should take far more than the current delivered by the 80A alternator for the wiring to be a limitation. If an 80A fuse was sufficient for use with the 80A alternator, there would be no reason for Toyota to install a 120A fuse on their OEM 80A alternator as is written on top of the 2000 and later V6 Taco fuse box (below). Educate me. What am I missing here?

The '04 V6 Taco uses a 120A ALT fuse on the OEM 80A alternator circuit:

 

With wiring you're more concerned with sheathing/insulation temperature rating than burn-through. That's why you can have a thick wire compared to the fuse filament and have the same current rating. You'll see current handling ratings on wire spools increase for the same AWG with higher temp insulation. You're correct on the fuse sizing.

When I upgraded my ALT, I just left the existing wiring alone and added a 4AWG wire in parallel. Not recommended, but figure I'm under the hood enough to notice a problem in the 2 feet of wire.

 

What can also effect the system's current capability is if any of the various connections build up resistance ether over time, either cable deterioration or just something making a poor connection. That makes the source (battery or alternator) supply more current then it otherwise would have to get the same work at the load. You can winch something then go back with your hand or an IR gun and feel/measure the temps at the various points and connections. You probably know this but if your system has that issue it'll show up as heat around the poor connection or crimp after a heavy current draw.

 

I agree with your thinking. If I do upgrade to any alternator rated at more amperage than the factory type OEM 80A alternator, I will do much the same but am inclined to put current protection on that 2nd cable. The only question in my mind is whether to use an ANL type fuse or a Blue Sea marine-grade waterproof circuit breaker on the 2nd copper cable from the alternator to the battery. Some guys such as yourself are running the 2nd cable with no protection and have had no problems. But just in case of a high-energy crash, I would rather have a fuse or breaker on it.

 

Absolutely! After a hard pull, the winch motor will almost certainly be hot to the touch. Duty-cycle comes into play for the sake of the winch motor/battery/wiring/alternator. When a CB (circuit breaker) pops, we were taught to first put our hand on it to detect heating. If the CB went to a fuel pump or was hot, don't reset it unless absolutely necessary. And not more than 1 reset on any CB. Same with wiring/connections. As a saltwater marine mechanic in New Orleans & Destin, I dealt with wiring corrosion on an all-to-regular basis.

 

I like my breaker. But I use it for outgoing.