1994 C280 Diagnosis

Two issues with a 1994 C280 with only 35K miles:

Check engine light has come on. I'd like to diagnosis this if possible. I'm going to take a wild guess that maybe the O2 sensor has worn out. From what I have read there is no simple method to read the error code like the way my Grand Cherokee can be made to flash the check engine light in a pattern. I did see something about making a device with an LED & resistor which applied to the diagnostic connector will flash with the codes. First of all, is this...

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...the diagnostic connector? Is there a diagram of which pin is which? Maybe there is a good site for this which I haven't found yet.

How much of a bitch is it to change the O2 sensor, should that be the trouble? BTW, the SRS light has been on for a long time but I'm more concerned with the Check Engine light as an emissions test is coming up.

Second issue:

For years this car has had a problem with the HVAC where it oscillates between heating and cooling, like during AC season it will cool nicely but eventually sense the cool air and kick it into heat mode. During heating season it eventually feels the warm air and starts blowing cold. Dealer checked it and said there is nothing wrong. Obviously they didn't drive it long enough to get it to do it (20 min or so). Any ideas? One thing that it *could* be in theory is that if the interior temp sensor came unglued from whatever it's attached to it would not have the thermal mass necessary to moderate the temperature swings. On the other hand even if that's not the case maybe applying some mass to it will correct for some other fault. So what I'd like to know is where is this sensor located and how do I get to it?

Reply to
Steve Kraus
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