I have a 1987 300TD w124 wagon and it has had a chirping sound from the dash for the last few weeks. It definitely sounds like a motor bearing/bushing on its way out. I assumed it was the air sampler motor (which previously had made some noises for me), but I removed that today, and the noise persists. You can hear it very clearly when outside the car, by the fresh air intake and monowiper.

Basically, if I have the car on, regardless of whether the climate control is on or off, I can hear this chirping/squeaking motor. If I turn on or off the heater fan, you can hear the chirping change speed as well, so basically I am virtually certain it is the heater blower motor. I think I have two distinct problems 1) the squeaking and 2) the motor running all the time. So a couple of questions:

1) Is it correct for the heater blower motor to run at low speed even if the entire climate control system is off? If not, does this suggest a particular failure for me to address? Maybe the fan motor brushes or a switch somewhere has failed?

2) Is there a consensus regarding lubing the motor shaft vs. buying a new motor vs. buying a new motor with squirrel fans attached? I am on a tight budget unfortunately.

I don't know about their relevance, but I wanted to give two more details about my car. My A/C is non-functional, so I have only been doing these tests with the heater on or off. And on rare occasion, the entire climate control does not respond to my pressing of buttons, until I raise the fan speed to high. This seems to remind the entire system to start working, and then the other buttons start working again. This last observation is not a big deal to me because it happens so rarely, but I wanted to share it on the off-chance it relates to my questions above.

Thanks for any help you can provide.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).