If you ohm it out and find similarities then you might find the correct connections otherwise I guess you have a 50/50 chance of success. Might as well get with it.

 

Thanks - good suggestion, that was the first thing I tried - but all possible pairs on that 2x2 connector had the same resistance. That's what led me to wonder whether perhaps it doesn't matter - but would appreciate any expertise as to whether that's the case...

 

When you ohmed it out did you reverse the leads to see if you had a different reading?
I have a spare for my Honda ES6500.
Tomorrow I will take some time and check it and see what I can find.

 

I found my ACR and it is slightly different.
Ohming it out will be no help to you.
Before you continue, you will be advised to find a schematic for your generator and determine how the AVR is connected.
I am going to look for your schematic on line.
Then you should find a correct AVR for replacement.
That being said you can take your chances as it may work like it is.
But the colored wires were done so for a reason.
At this point I want you to look at the pin end of the connector.
If the pins are flat you can see a spring catch that holds the pin into the plastic holder.
Find a small scribe or a tiny screwdriver, push the wire into the holder and hold it while you push the catch spring in enought to allow the pin to be removed from the plastic holder.
This should be done in a careful manner as you do not have a pin removal tool.
Once you have the pins out (all four) you can then replace them in the proper sequence.
You said the ohm test did not reveal any directional flow of the voltage.
This would indicat no diodes were found.
Better be sure of your readings.
As for the black and red wires, push the pins out if you want but if the original two pin holder has female pins, then just use them as they are and push them on the generator pins.
There may be a problen later as the plastic holder has a lock that helps prevent vibration from the pins seperating.
You may have to cut and splice them.
You have the option of trying it as it is and go from there.
I would send the new AVR back and keep lookng for a correct one.
You were wise to take pictures as that will help later.
Sorry that I could not be of more help.

 

You obviously have done some research.
I looked here first:
I looked further and my first find was here on Amazon:

Amazon.com: Stable And High Generator Avr Generator Volt Regulator Universal Avr for Generator : Automotive

Buy Stable And High Generator Avr Generator Volt Regulator Universal Avr for Generator: Voltage Regulators - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

First things first.
The AVR is designed for the KW rating.
I used your 6.5 kw as a guide.
I noticed that you have a molded AVR with a heat sink on the SCR. That is important.
Next I took notice that all AVR's seem to have the two wires red and white or black.
The red wire should be the positive wire and the white or black is the negative.
I would keep my attention on the proper placement of the white and blue wires in the plug.
$15 is not a big deal if you are in doubt.

 

Try this:

Set your multimeter to test diodes and put the BLACK probe on the AVR's Red wire. Use the RED probe and check each of the Blue and Yellow wires and see if you can get a half a voltage drop to appear on the meter.

If you find it, that color pair (whether it's Blue and Blue or Yellow and Yellow) would be for the excitation winding. That means, the remaining pair would be the sense wires.

Do the same procedure on both AVRs to see if their relative position on the connector is the same.

These AVRs are made by different manufacturers in bulk. They don't often adhere to wire color codes. Even the wires that goes to the brushes are oftentimes not color-coded correctly.... and those are polarity-sensitive. Most would have a tag that tells you which one is the positive (+) wire going to the brush.