A/C blower and funny diode

Following advise on other threads I traced an a/c compressor not engaging issue to a split wire that goes from the compressor to the relay and passes right next to the manifold. The wire seemed to be split right where it enters a little plastic white box that has a diode inside it. My a/c service man simply excluded the box with the diode and bypassed the wiring. After a charge of R134a it seemed to work just fine.

However, after a short stop I tried to restart the a/c and found that the blower wouldn't blow. The compressor kicks in fine. I moved the cables and got the blower to work on three of the four speeds but when I take it to max, the blower just quits. A couple of years ago my fan speed switch lost the detents from one speed setting to the next. It kept working like a progressive switch which didn't bother me at all.

Anybody know what this diode is for? Is there any wiring from the compressor to the relay that affects the blower? I suppose if my fan switch was at fault moving these wires would have no effect. When it works the blower sounds great and blows strong so I don't think it's time yet to tear into the evaporator. Any clues?

Thanks,

Maurice

actually it's a variable resistor, based on the current from the reostat switch it meters it's power to the fan.,..I wouyld replace the switch

actually it's a variable resistor, based on the current from the reostat switch it meters it's power to the fan.,..I wouyld replace the switch

I really appreciate your answer although much to my regret, I still don't get it. The box with the diode is a variable resistor that "meters" power to the fan. By "meters" I would understand "measures" or maybe "selectivelly delivers", which would ultimatelly imply that this resistor is directly related to fan operation and delivers power according to the reostat switch (fan speed switch?) position, right?

If this is so then I don't understand why you would suggest I replace the fan switch when the most logical thing to do would be to reinstall the resistor on the line. Please correct me if I'm wrong.

Thanks again.

Maurice.