For car up to 85. When adj idle co. Connect analog voltmeter negative lead to x11 #3 pin. And posittive lead to battery+.Disconnect o2 sensor plug. Observe voltmeter reading. Place a tape on voltmeter and mark center of the needle. The needle should not be moving. RE connect the 02 sensor.The needle should vibrate around the center mark. If not . Adj co to center the mark.That is. From 86 up. Use DUTY CYCLE. Hope this help.

Erubin, it is a 1985 500sel, I am using the "famous" Sears multimeter that a lot of members here have. I don't think it is faulty. Is it possible that you can use your Actron reading your car's current duty cycle? I am curious, maybe it is right at 22% again.

Like Andengines responded, I think what he says is exactly what I meant to ask.
I do look at the voltage adjustment the same thing as duty cycle adjustment though.

the last time i checked i got battery voltage on my DC digital voltmeter and about half of what I expected for the duty cycle. Neither reading made sense so i abonded my meter and went with one that a former MB tech used on early 80s systems. Sorry I can't help more as i am done witht his car.

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1972 450SL
1982 300D Turbo

erubin, I disconnect the O2 sensor underneath the car. The duty cycle read 25%.

With O2 sensor connected, duty cycle is adjustable and my current setting is very close to 25% up and down. At 2500rpm, it leans to 30%.

I guess the answer is clear to me now. I think there's nothing wrong with your Actron. Our cars are supposed to behave like this, like andengines has described.