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Warning: AAW Alternator brown resistance wire

32K views 36 replies 19 participants last post by  lamburgey 
#1 ·
Thought those who have installed or are going to install an American Auto Wiring (AAW) harness in their Tri-Five Chevy might be interested in the need for adding resistance to the brown alternator exciter wire in the AAW harness, especially with an early 90’s GM CS130 alternator. As an aside, I don’t have an idiot light in my install, and don’t get the resistance drop the light provides.

When I checked with AAW, Donny said, “we found out through lots of research that the CS alternators need a higher value resistor than what is in a stock harness of our Classic update kits. The brown wire already has a resistor on it, yes, but needs more. Without the higher value, you run the risk of damaging the regulator. That is why we led folks over to the other (SI) adapter. If you want to splice your own resistor in line, call the tech line and they should be able to give you the value of that resistor.”

I have a connection plug for the alternator, but there is no added resistance in the wiring. Turns out there are two connection plugs, one with added resistance, and one without.

When I called the AAW tech line, the tech told me the brown wire essentially had no resistance, and that I needed to add a resistor. He said he usually uses an 87 ohm resistor, but when I told him the GMPP installation manual calls for 50 ohms, he recommended adding that resistance.

Acardon wrote me: “If you look at the wiring diagram on sheet 3 : http://www.trifive.com/92965107 500435 IN 3.0.pdf You will see that the brown resistance wire (dashed line) from the accessory terminal, ties into the solid brown wire from the idiot light. This puts the light bulb and resistance wire in parallel, causing a drop in resistance, not added resistance. It's been my understanding that the extra resistance wire was a back up exciter for the alternator, in the event the bulb burned out or for voltmeter vehicles.
This is a pretty good article on the subject of converting to a CS alternator. http://www.novaresource.org/alternator.htm”.

Acardon had me measure the resistance from the accessory terminal of the ignition switch to the brown wire of the alternator plug with it unplugged, to isolate a measure of the resistance of the brown resistance wire. I measured 10.4 ohms, Don’s neighbor measured 10.5 ohms on his AAW harness.

As a result, I wired in a 50 ohm/5 watt resistor I had, in series with the brown resistance wire, yielding a total of 60 ohms of resistance. The novaresource post Acardon cited recommends between 35 and 350 ohms.

Thanks so much to Acardon, AAW’s Donny, and Roger1, for figuring this out.
 
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#2 · (Edited)
Kudos to Belair-o for finding out about this issue.

I have 2 vehicles with AAW Classic Update harnesses and CS130 alternators.
One of the things I did when I got my first harness was review the main diagram and saw that a resistance wire was provided for the alternator excite. I assumed that since the AAW Classic Update harness was designed for modern components, it would be the proper resistance needed. That assumption was wrong and the fact that AAW doesn't provide some sort of note in their instructions about this, is a major oversight IMHO. Since the SI alternators have been obsolete for over a quarter of a century in favor of the CS type, AAW should have even provided an option for the CS with the kit. It is after all, an "UPDATE" harness.

When Belair-o first contacted me about this I thought there was a mistake somewhere but no, he was indeed correct. I've already added a 10-watt 50 ohm resistor to one of my vehicles and will do the other soon.

Very important issue. I think this thread should be made as a sticky in this section.
 
#4 ·
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#9 ·
Also, unless AAW has modified their harnwss design, their alternator harness has the sense wire from #2 terminal attached with a short jumper to the 12V terminal on the back of the alternator. A.K.A. a 1 wire set up. For the sense wire to get a true reading of system demands it needs to run forward to a distribution point on the firewall.
I did this when I rewired the engine compartment on my wagon. The needle used to jump when the blinkers were on, now because it can see the whole system, the gauge stays steady with no fluctuation.
Mark
 
#10 ·
#18 ·
Two (dumb?) questions about a three wire alternator.

1) Can the remote sensing wire be simply connected directly to the battery terminal?

2) Does having an LED indicator dash light affect the alternator's operation?
 
#33 ·
I Burned up my alternator on the new crate engine I installed and after much research, this problem seemed to cause the issue.
I replaced the alternator, added the resistor and all has been well every since. I did not use the idiot light and didn’t have a volt meter installed at that time, so I had no resistance in line.
Bought the resistor from radio shack. They came in a package of about half dozen, so if anyone needs one, I’ll mail you one...
 
#34 ·
If your running an MSD Box don't you need the Resistor on the Brown Wire from the Alternator to stop the engine run On. Seems hat without the Resistor the Generator LIght emits a soft glow when the key is turned off allowing the engine to run on. The resistor creates enough resistance to stop the run on and it seems its also needed with the new AAW kit as well.
Did I read all that correctly?
 
#35 ·
I have an issue on my 57 that I have tried to solve for the last couple of years with no luck. SI 110 amp 3 wire alternator and AAW classic update wiring.
Problem is that it seems after the car is warmed up the gen like thats in dash comes on intermittently at low(600-1000)rpm. Higher rpm and it goes out. Comes on also when I turn headlights on and wont go off until high rpm or sometimes just a dim glow.
Yes I have checked volage from alternator when this happens and I am getting 14.5 volts. Alternator is charging fine and battery doesn't run down.

I stumbled across this thread and wonder if I need a diode installed?
Any thoughts?
 
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