1989 300e electrical question

[dbcooper]

Greetings

My one owner W124 has been has been a great car over the years but is now asking for some attention.

For the last several years, once in a blue moon the warning buzzer with momentarily activate when the brake pedal in pressed first thing in the morning. Pressing the pedal a 2nd, 3rd, 4th.... nothing unusual happens. No big deal to me, just something interesting. I figured the car had a poor ground somewhere in the brake light circuit and was back feeding the buzzer with current.

One months ago the 10 old battery finally gave out. I did jump start the car to get home.

A few days later I noticed that sometimes the check engine light on would sometimes remain on after the key was removed. It does not happen immediately every time. The light goes out when the engine is started and the cars runs normally. I have not fully tested the Over Voltage Protection ( OVP) relay yet. I can confirm that my car will car will crank but not start without the fuse present in the relay. I am planning on replacing it as cheap insurance.


PART TWO

I think the key sensor in the ignition lock is broken. Before I jump started the car when I had the dying battery, I was removing the key from the lock and was suprised when the warning buzzer stayed on. When the door is shut the buzzer goes off and stays off when the cars is driving. I tried to remove the lock by turning the cylinder to position 1 (acc) and inserting a piece of coat hanger. It goes in several centimeters but the cylinder is not released; despite lots of wiggling. Do I have to unthread the black position indicator collar first? I am going to try applying some vibration to the cylinder with a electric sander to see if that will help.

Anyone ever had these symptoms? Any diagnostic suggestions?