Here's one for those that like a good mystery

2000 C230K 155,000 miles

Problem first arose two weeks ago when the rear window defrost would not work, then work, then not work etc. Searched the forum and more likely than not, it may be the defrost relay. But could it be more?

A few days ago I noticed that the auto door locks do not engage all the time (At about 9mph the locks should lock). I can manually lock the doors from the switch on the dash or the key and if I do, when I stop, park and exit from the car, the disengage when I open the car door. Again, this does not happen all the time, but more than not.

Then today when I put my ignition key in the hole, it will not "click" to unlock and engage the system. I have to pull it out, reinsert, try again etc. Sometimes it will work on the first try, other times the 10th. I tried the valet key and it works much better, but never 100% of the time.

So what's going on here? I've really had little to no issues with the car for a while, but now it's like the gremlins have got it. Could it be a relay (Is there a master relay?) and if so, which one? And why three very unrelated issues and none of them all at once?

Pour out your words of wisdom and I'll be greatfull forever!
Thanks

Check the battery and its connections first. A failing battery can show some peculiar signs. Other than that, your car shares very little with mine so I can't offer anything.

Tested the voltage of the battery early this morning in 28 degree weather. Good static voltage (no issues under load as well). For now, I can rule out the battery.