1995 E320 Sedan (W124)

About a month ago my A/C starting having problems. It has always worked like a new car. About once a week, when I started the car, the A/C would not come on at all. Then, 10-15 minutes into my drive, the blower would suddenly come on full blast. Now, for the last week. Whenever I get it the car, it rarely starts right away. Sometimes I'll start it in the morning and it works fine. I will stop at the post office to pick up my mail, start the car again and it won't come on. I have no idea what would cause this intermittency. Tonight, I started the car, the A/C started blowing, I turned off the radio, and could hear a light grinding/purring coming from in front of the dashboard, right where the windshield meets the hood. I am scared it might be the blower motor going bad. I hear that's an expensive fix. But that doesn't explain why it sporatically operates. Please advise.

Thomas

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'95 E320 Sedan w/224K Miles (W124)