Stand alone harness to stock wiring

[Rodder4hire]

I am wiring up my 8.1 Vortec swap. Pcm has red blue plug combo and is almost identical to red/blue plugged ls. Modifications to stock engine harness according to LT1SWAP.COM.

I have it all wired except the brown and brw/wht wire that originates at the acc terminal of the ignition switch and terminated at the voltage regulator.

Standalone harness seems to have all the wires to alternator accounted for other than b+.

The brown feeds the accessories also. Where is this power applied from? Does it come through the switch from pink to brown? I'm pretty sure not.

Can someone lay some knowledge on me?

[MARKDTN]

The fuse block has both ignition switched and battery power that is unfused.

http://67-72chevytrucks.com/vboard/s...d.php?t=638067

You could work with that.

[Rodder4hire]

According to the wiring diagram, red is unfused battery power and orange/purple is keyed (I switched this to 12 gauge non resistance and pink). Brown 12 gauge went to the voltage regulator. Is brown unfused power also?

[Rodder4hire]

According to the wiring diagram, red is unfused battery power and orange/purple is keyed (I switched this to 12 gauge non resistance and pink). Brown 12 gauge went to the voltage regulator. Is brown unfused power also?

[Jason Banks]

I'm attaching a wiring diagram....should help you...

Looks like brown is switched power that feeds the fuse panel...

[Rodder4hire]

Thanks. I have a giant diagram on my garage wall. It unfortunately doesn't answer the question I posed.

[Rodder4hire]

Let me rephrase my question. Does the large brown wire that attaches to the top terminal (on the diagram) of the voltage regulator RECIEVE power from the accessory terminal of the ignition switch there or does the voltage regulator PROVIDE acc power to the ignition switch?

No diagram shows me which direction power is flowing and I don't have a grasp on the internal workings of the regulator.

Please and thank you!!

[CarlsLQ9SS]

This might help answer your questions.
http://67-72chevytrucks.com/vboard/s...d.php?t=119379

[Rodder4hire]

Kinda. The brown is the crucial to conversion to internal reg in a stock situation. Unless I'm mistaken, my 8.1 vortec harness and stock 8.1 alternator takes care of all that.

I'm desperate to find out if I need power to this wire to run the heater and others, or if turning the key to acc position sends power through the switch to the heater and others.

In other words, with a stand alone harness, do you need to put pink keyed power to the brown regulator wire, eliminate it, or put battery power to it since its hot when the key is not in the start position.

[MARKDTN]

Are you looking for coil power to your swap or an ECM trigger?

In later GM wiring, pink is accessory wiring. It gets power when the key is in run or accessory. In 67-72 is is ignition power from key to the firewall, then it changes color to a resistance wire to the coil (so not 12v) so only gets power in start and run. Brown is also ignition switched. It gets power when the key is in run or accessory. To your question power flows from the switch from the brown wire to the regulator-but-it goes through a light on the dash if you have a idiot light dash. You may want to use that for your alternator if you want a charge lamp. If you want reliable accessory power trigger to the PCM to tell the computer that the ignition is on, I would go back to the fuse box and use the ignition power unfused lug. If you want coil power, use the pink wire to the firewall bulkhead but change the wire on the engine side to eliminate the resistance wire.

[cj847]

I am relatively sure (90%+) that the brown wire is 0V key off and +12V key on. However, on some models that wire is a resistance wire which will result in lower voltage at the bulkhead. I would not use it. And to your question I think you can eliminate it.

[RichardJ]

>>I have it all wired except the brown and brw/wht wire that originates at the acc terminal .................................................................................................... ........................................................

The brown feeds the accessories also. Where is this power applied from?<<

The power comes from the Battery, so start at the junction block and follow the Red wire through the bulkhead connector. The Red wire feeds the Always HOT fuses and posts, but also continues on to the Ign Switch. The Pink wire is not part of the charging circuit. This is HOT, from the Ign Switch, key ON ONLY.
I removed all the wires from the schematic that aren't part of the charging or starting circuits.
With the key ON, 12 V is applied to the brn/wht 10 Ohm resistor wire. Through the bulkhead this wire is connected to a brn copper wire that was originally connected to terminal #4 of the Voltage Regulator.
If a SI Alt has been installed, this brown wire would be connected to SI terminal #1.
The second image shows the brn/wht resistor connected to one side of the Gen Lamp and both tied to a single Ign Switch terminal. The other side of the resistor tied to the other side of the Gen Lamp at the bulkhead.
If not used, the Gen Lamp can be simply cut out of the circuit. The 10 OHM resistor wire must be there because it is part of the SI alt AND the DN ext reg alt.

The 3rd image is from someone on this forum that says this works. I don't know. The 10 Ohm in the original dash harness plus 85 Ohms equals 95 Ohms, which is in the range of what I have read for the CS alternators. I only mess with the DN and SI alternators unless the vehicle already had a SC like my Vette had and I had to replace the alt 3 times.
Note that in the drawing the SC has S,I,L P terminals plus the Batt terminal.
At the beginning I said the pink wire was Hot with key ON only. I've seen the S terminal on the SC wired to switched power with key ON. The image #3 shows S hot at all times. I've seen both from the same web source.