Alternator Wiring for House Battery

[realfstkid]

Hi Guys,

I'm about to install a house battery under the back seat in my camper, and I'm trying to get a feel for how the alternator wiring is set up. I've got a Bosch AL33X alternator which has two red wires (same connector) and a blue wire. One red wire goes to the starter, where it's connected to the heavy gauge starting cable that runs to the starting battery. The other red wire and the blue wire run toward the front of the vehicle.

Here is the wiring diagram for this part:

Where do these red and blue wires go? I'm assuming the blue wire is the alternator warning light from this diagram:

So as far as this alternator is concerned, is the voltage regulator measuring voltage as it sees it from the output terminal? Is this not the most ideal case, since you have to account for voltage drop in the cable due to the current flowing through the alternator? Don't some alternators have another wire that senses the voltage at the battery terminal (wire to terminal w/o current running through it)?

These questions are all posed to better understand how the alternator is determining what voltage to supply, and what voltage is actually being supplied to the battery. Also, I need to tap into this circuit for my house battery (connected through a relay or isolator) to receive a charge from the alternator when the engine is running.

Thanks
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1987 Westy - "Vivian van Fuego"

[MarkWard]

I need to see current track 33 to tell for sure where the second red cable goes.

Blue wire is the lead for the alternator indicator light.

[realfstkid]

[crazyvwvanman]

The larger red wire from the alternator to the starter is the main charging wire.

The other red wire from the alternator powers the fuel injection system and nothing else.

In general it is safer to connect the aux battery charging wire to the starter rather than to the alternator. Then run a booster wire from the alternator to the starter, 8 AWG or 10 AWG.

Mark

[Altoona]

The other red wire is the fuel injection power supply. Goes to the black box at the front left corner of the engine bay.

[realfstkid]

[MarkWard]

One good size wire between the Alternator and the starter solenoid is adequate. Connecting the auxilary battery to the starter solenoid shortens the run so less voltage drop due to the distance.

The alternator is internally regulated. The blue wire is used to excite the alternator into charging. The load from the dash warning light is adequate for this. This circuit is also connected to the isolating relay for the kitchen under the driver's seat if equiped. This keeps the fridge from running on 12 volts when the engine is off and quickly draining the battery.

[realfstkid]

Alright, here's what I've come up with so far for a wiring diagram for the system, which I'm in the process of re-doing...

Any thoughts?
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1987 Westy - "Vivian van Fuego"

[KBM]

What came of the set up?
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Annie a 87 Vanagon Camper - 2.1 Auto 2W

[Ronzo_volvo_guy]

RFK;

I agree with Mark...he has it right!...some Alternators (like in boats) are not local to the Battery, so the VReg has a separate wire for "Remote V Sensing". Given heavy gauge wiring, and Clean and Tight!, that is not necessary here.

My thought on your diagram is that I would love to have a closer look at it, but when I click on it it gets even smaller, not bigger...I could import it and blow it up on my machine, but it is possible to upload a bigger file to this photobucket hoster, so I don't have to sit on my keyboard?

Cheers

[harvgwen]

That diagram is 8 years old.
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1986 Westfalia Vanagon, 2.2 Subaru
Okanagan Valley, British Columbia