Yes, I live in Canada, but it gets hot here too

My A/C is not working, and I really need to get it fixed fast . . . the black interior is unbearable without any relief from the A/C . . .
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THE CAR:
- 1993 Mercedes 300SE (W140 S-Class)
- 50,000kms (31,000miles)
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THE PROBLEM:
- Start the car
- A/C is blowing fine. Nice and cold, and really strong when on the MAX setting
- Pop the car in drive
- Start to drive
- All of the fans power down after about 10 seconds! (although the trickle of air coming out is still cold)
- Come to a stop light
- As soon as the car stops, the fans fire up into MAX mode again
- Light turns green
- Car goes into motion
- Fans power down once again
- And so it continues . . . car stopped = fans on . . . car moving = fans off
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MEASURES TAKEN TO TRY AND DIAGNOSE:
- Ran the A/C self diagnositics . . . no fault codes show up
- Changed the pollen filter . . . did not help
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POSSIBLE DIAGNOSISES I HAVE HEARD OF:
- Faulty Blower Regulator ($288CAN or $180US)
- Faulty Temperature Sensor Unit ($48CAN or $30US)
- Pollen Filter (already replaced this, so that's not the problem)
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Can anyone please help me out here? I would really love to have the air conditioning back! Please please help
Thanks in advance,
Bryan