I got out my DMM to re-test the O2 sensor voltage last night only to discover that it would not read DC volts even with a new battery. So off to Sears, where I discover a DMM with Duty Cycle on sale for $29.95.

Take a break from my day job and test the O2 voltage - very low, fluctuating around .005v. No change in the on/off with the sensor disconnected. Still sits at 10%. This reading is coming from the dwell setting of my Sears engine tester which I have used to test my 300E, Hbofinger's 560, and several other cars.

But, since I have this nifty new DMM, I decide to try out the Duty Cycle function. Lo and behold, I am getting a fluctuating 55-65%. Still no change with the mixture adjustment, though.

So now I am thinking 1) the dwell method does not work on this system for some reason, 2) maybe the brain is still alive, 3) the O2 sensor is possibly/ probably dead.

So - I will order a new O2 sensor and try this again. It's not clear why this one would fail in just over a year and a couple of thousand miles.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe