Honda Civic 96, stock 75A Mitsubishi alternator

So I did the Big 3 upgrade, and I haven't and still contemplating to fuse the positive 4 AWG wire between alternator and battery terminal. I have a 75A stock alternator. The gauge-4 wire is rated up to 120A max. So the whole point of putting a fuse to protect the wire seems irrelevant.

Common perception is you fuse a power line all the time no matter how oversize the wire is. Reading through the internet, it's an open debate. Most people will say fuse it, if the main reason for protecting the wire from excessive amps is out of the equation, another logical reason given is because of constant vibration or worst case scenario when you get into a wreck, the ring terminals either in the battery or alternator may come loose and weld/burn up things when it connects to chassis ground. If there's a fuse, it should pop during a short circuit and protect. Valid point.

However, the same argument could be said with fuse holder/fusible link. At least from what I'm have. Wouldn't a properly crimped ring terminal on both ends of the wire be a lot more secured and has less chance of breaking loose than a bolt squeezed wire on the ends of these ANL fuse holders? Worst case scenario is you now have two wires (battery to fuse holder, fuse holder to alt) that may dangle.

What are your thoughts? I fuse power wires all the time, but that is to protect wires that may be undersized for overamp conditions. In this case, when it's not about amps and it's about sturdiness of the terminations, I still fail to convince myself I should install this.

 

Pro - Fused line.

Con - Unsealed break in wire / crimp connection, allows moisture and current to cause corrosion issues faster and more often than a solid one piece of wire.
Con - Fuse Blows, takes alternator with it.

 

Not a good idea.
When the fuse blows then the alternator will blow.
Don't do it.

 

Appreciate your replies. Can you explain to me why would the alternator be affected if the fuse blows?

 

Yeah that's pretty simple really. There's no place for the current to go if the wire breaks aka fuse blows.

So it will fry the internals of the alternator, either the rectifier or the voltage regulator or both.

It's sort of the same concept that happened to a lot of my electrical devices that were plugged in when the ground wire got knocked off the telephone pole when I lived in Florida. It doubled the voltage as both hots were coming in and there was no ground to take it away.

Same basic thing will happen if you break the connection to the battery. The battery essentially acts as the "earth ground" by sucking in the current from the alternator. Without that line, the current has no where to go but the internals of the alternator.

I hope that makes sense, it's probably not explained the best but hopefully gives the idea.

I could be mistaken as I am not 100% sure what safe guards have been incorporated into the alternator as I'm pretty sure you can disconnect the battery with the car running and most cars will run fine on the alternator alone. But I also remember what happened in Florida and I could see something similiar happening in this case as the connection to the battery could potentially do the same thing.

A lot really depends on how the circuit was designed. I think I remember seeing someone mention that pulling the battery on a civic can fry the alternator so I tend to think it's similiar to my AC incident in the residence.

 

Can you please identify which specific terminals you're talking about here^.

 

It's the crimped ring terminals on both ends of the gauge 4 wire I added between positive battery terminal and altermator. Most people say due to vibration or a wreck it MAY come lose and a fuse should be an insurance against short circuit.

 

I forgot to mention that the stock wiring is intact. Thanks for the explanation. Made sense. However, looking at the stock wiring, Honda fused it with an 80A. If this popped, wouldn't it be bad for the alternator?

 

If that fuse blows you have bigger problems. At that point the alternator is expendable.

 

If the alternator side of the large wire were to come loose and to ground to the engine or chassis, then you are already protected by 80A hood fuse 41, which would blow in this scenario and protect you from what you fear.

That leaves the hood fuse box connection of the large wire. In this case, a simple solution is simply to check whether the bolt securing the wire is tight as part of your regular car maintenance.

 

No, because with the 80A fuse blown, the voltage regulator, ELD, ECU, etc. would no longer receive voltage, causing the engine to stall and the alternator to stop charging.

 

If you did upgrade the Big 3 then you should be OK?

And big kudos on using the 4-gauge wire. I honestly attempted using 2-gauge wire on another vehicle. I can tell you that the wire was too thick, and did not properly work as intended.

I just wish that there was a 3AWG wire..

 

if you disconnect the lead from the alternator, current simply stops, it doesnt somehow build up current until it blows up, now if you disconnect the battery with the car running, then the balancing load on the alternator is gone, and there will be high voltage spikes through your electrical system, but in this case the alternator still has a complete circuit where current can flow. The incident with the neutral lead on your ac system is a completely different scenario

 

I don't have a current sucking aftermarket sound system that usually precedes the big 3 but I couldn't believe how the Civic is running a lot better after it. It's a long story, but I did it because my A/C is acting up. I found out that the A/C clutch coil is only getting around 12.15V on cold start where battery voltage is 14.2. The voltage drop is simply too much and on a hot day or too much idling I'm sure it goes less than the operational voltage of the coil. So I 're-relayed' everything (clutch coil, horn, fans) and did the big 3. I bet all the sensors are also happier now hence the smoother run. Battery voltage at cold start up is 14.45v, around 14.1V at operating temp, 13.9 with accessories on.

 

Electricity is lazy, it follows the path of least resistance.

Source: My father.. Electrician.

 

I did the Big 3 because of significant voltage drops I observed everywhere in the system. Before, the stock wire between alt and battery had an unacceptable 0.5V drop with headlights and accessories on.Yes, the A/C scenario was a different story but that somehow lead me to the big 3 because it's also about voltage drop. I found out that measuring voltage on the battery terminals does not give out the true story and often times very misleading when troubleshooting electrical issues. Backprobing on the other hand gives you an accurate reading and not just voltage potential. I stripped the wires at the clutch coil then while it's engaged, backprobed it and I got very low voltage reading. Pretty sure it drops to inoperable levels when the resistance goes higher as engine bay temp rise. So far so good, it's summer over here and while I got stuck in traffic this past week, the A/C didn't bailed out on me.

Back to the big 3, I installed relays for the horn, a/c clutch coil, radiator and condenser fan. Horn sounds a lot louder (and meaner ;-)), the fans draw a lot less current because of the higher voltage. The big 3 is just the cherry on the sundae I guess.

 

Amen. Thinner wires and heat increases resitance. Power is current times the AVAILABLE voltage. Less available voltage and your components will try to suck more current to compensate. But a thin wire can only carry a certain amount of current. It sucks that manufacturers put the thinnest wire possible and not consider voltage drop due to corrosion and age.

 

Thanks, I'm not fusing. Glad I asked here first. I'm less worried about the crimped ring terminal on the alt side because there's less tension there compared to the one that goes up to the battery. It curls around a bit so even if I trust the crimping, tension and vibration is a concern. Pulling it from time to time as a maintenance check would make it worse I guess. I just bought a nice battery multi post for the positive terminal. No need for ring terminals and crimps but it lies flat on top of the battery and the wires go deep inside and a huge headless allen bolt secures the wires. This I can check and tighten regularly.

 

Trying not to laugh at how this went down, and whom educated then got schooled...