Wire From Alternator To Battery

[Super Cracker]

My Explorer came stock with the 95 amp alternator which just isn't cranking out enough juice for the stereo I have. I'm looking at upgrading to the 130 amp version which from my understanding will fit, but in addition to that I'm also adding an additional run of wire from the alternator to the battery.
My question is if it's safe to run a length of 4 gauge wire from the alternator to the battery (fused, of course). I believe the current wire runs from the alternator to the starter relay and plan on leaving that one in place. Would it be possible to run that additional wire straight to the battery from the alternator?
I've got a 96 Explorer XLT with the 4.0 V6 in it.

 

[roscoe 0202]

you are basically running the wire to the battery if it goes to hot side of starter relay so it would not make any difference to wire straight to pos side of battery.
roscoe

 

[Jason94sport]

The factory 130 isn't a big upgrade you don't really need to do anything for it. I ran the 130 on my 93 for 6 years.

 

[Super Cracker]

you are basically running the wire to the battery if it goes to hot side of starter relay so it would not make any difference to wire straight to pos side of battery.
roscoe

Alright that's what I was thinking but I didn't wanna go messing with anything and mess something up without being 100% positive.

The factory 130 isn't a big upgrade you don't really need to do anything for it. I ran the 130 on my 93 for 6 years.

If it was only that I was upgrading the alternator then I probably wouldn't think anything else about it, but I've got a stereo in the back that I have to power. I've got 2/0 grounds (leftover wire from my dad that he never uses) and the current cable is kind of dwarved by that. It's essentially just trying to reduce the voltage drop when going full tilt with the subs.

 

[CDW6212R]

The alternator power wire goes to the Power Distribution Block, the PDB, which already has a built in mega-fuse(there are two terminals there.

You have to know which V6 you have, each of the two takes a different alternator. The OHV 4.0 takes the same 3G alternator as the 1st gen Explorers. The SOHC 4.0 takes the 4G alternator, the same one in all 96-01 V8 Explorers. The mounting is different in those, and internally they aren't wired the same.

Run your new wire along the same path as the old one. You can remove the old one, but it's fine to simply attach the new one on top of the existing connections. I did that with my 99 truck in 2006, since I have an on board 30amp air compressor. I think I just added an 8 gauge wire, the bigger wires will take special terminal ends to attach those.

 

[Super Cracker]

Alright so I put the new 130 amp alternator in and ran the new wire, leaving the existing wire attached to everything it should be. When I put a decent load on the vehicle at idle (blower, brights, auxiliary lights, wipers, brake lights, etc), the voltage will remain about 14.5 up until it hits a certain amount of current being drawn, and it's almost like the alternator shuts off because the voltage will drop suddenly to 12.8 and just keep dropping until I remove some of the load. However, if I bring the engine to 1500 rpm or higher, it's perfectly fine until I bring it back to idle, at which point it will drop back to 12.8 volts or lower after about 30 seconds.
I have the Ultima 130 amp 3G alternator and I have the 4.0L OHV. Does this sound like a voltage regulator issue? I have no earthly idea what might be behind this. I know higher output alternators have lower outputs at idle but this is ridiculous.
Also when I start the vehicle it'll sit at 12.5 volts for a few seconds then slowly climb to 14.5.

Edit: After a bit of research, I'm wondering if it maybe isn't a bad diode.

 

[BKennedy]

I have a 1994 year model. I upgraded to the 130 amp alternator many years ago and have two batteries. I still have the factory wiring to the starter relay. Both are being charged at 14.5 volts. When I put a heavy load (two LED light bars, aux trans cooler fan and 3/4 HP air compressor) on the auxiliary battery, the volt meter drops to no lower than 13.8. I usually don't run everything at the same time.

You might have more of a battery not being able to take the load issue than a alternator issue. What battery do you have?

 

[Super Cracker]

I have a 1994 year model. I upgraded to the 130 amp alternator many years ago and have two batteries. I still have the factory wiring to the starter relay. Both are being charged at 14.5 volts. When I put a heavy load (two LED light bars, aux trans cooler fan and 3/4 HP air compressor) on the auxiliary battery, the volt meter drops to no lower than 13.8. I usually don't run everything at the same time.

You might have more of a battery not being able to take the load issue than a alternator issue. What battery do you have?

It's an Autocraft Gold group 65 850 CCA. Just replaced the old battery within the last 6 months so I don't think it'd be the battery.

 

[J_C]

I may not understand what you're saying but it seems like it's just that you're drawing more current than the alternator can provide at low RPM, so instead of a higher voltage than the battery (which would charge it), instead you're draining the battery.

If that is the case that is not a sign of any fault per se, just that you need a higher output alternator if you want to draw that much current at low engine RPM, or a smaller diameter pulley so it's spinning faster at idle.

Here is an alternator test report that came with the 130A alternator I put on my '98 SOHC a (couple?) years ago. Note that RPM on it is alternator RPM not engine RPM.
It's just the standard Advance Auto Parts Carquest reman they sell, nothing special.
Advance Auto Parts - Down for Maintenance

 

[BKennedy]

Why do you need to run all of that stuff at the same time? I never run the compressor and light bar at same time because there is no need. When I am running the winch, everything that I don't need at that moment is not running. I can run the blower and other stuff because they are on separate batteries which helps absorb the load. You are pulling so much power you are overwhelming the system. Its not good for the system, and unnecessary.

 

[CDW6212R]

Ditto, the alternator is likely not keeping up with the loads. I'd have the alternator tested, that should identify what the idle capacity is, and at what rpm it runs best. Some aftermarket alternators produce less amps at idle than stock, but others make more.

It isn't one or the other, some help and some make things worse. The two I've bought work a little better than stock(these are 4G's), but not much, and I don't run much beyond stock loads right now anyway.

 

[Super Cracker]

Went and had o'reilly's test it and the guy there said there was a bad diode in it. Got the money back and went to Autozone and got a Duralast brand instead of Ultima and there isn't any voltage drop unless I blast my subs full tilt.

Why do you need to run all of that stuff at the same time? I never run the compressor and light bar at same time because there is no need. When I am running the winch, everything that I don't need at that moment is not running. I can run the blower and other stuff because they are on separate batteries which helps absorb the load. You are pulling so much power you are overwhelming the system. Its not good for the system, and unnecessary.

The stock 95 amp alternator ran all that stuff just fine so I figured that a 130 amp should produce enough current at idle that it would also run all of that. Just the combination of having the blower running with the headlights on would cause it to drop from 14.5 to 12.8 until I turned both off.

 

[CDW6212R]

You could install a smaller diameter alternator pulley. The OHV 4.0 doesn't turn as many rpm's as the SOHC, so the alternator will be fine to run a little faster. That will help the idle current more than anything.

 

[BKennedy]