The cable is used to hook up a milliamp meter in series with the EHA. You measure current in milli-amps, not voltage. Should be 0 mA at idle with the mixture set correctly -- set it with the 3mm screw fitting in the fuel distributor.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Ah yes, the old, i got in a hurry and forgot trick. I was using voltage settings, I was in a hurry to use my new test harness tool thingy this afternoon and only had about half an hour. Ya, I remember now and I can do the test in mA. I just forgot, or I got in too big of a hurry more like it.
It should be at 0 mA at idle with the engine warmed up and the o2 sensor warmed up and working correctly ( signal fluctuating back and forth ) Right?

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red