Motor Speed Controller diagram

Hello everyone,
Noob here. I'm trying to connect a used wheelchair motor to a power supply but I keep burning the speed controller (3 so far). I connected the motor this way and it will run for a few seconds to a few minutes. When I dial the speed down and try to dial it up again it will cease to run. The speed controller gets hot and a chemical smell emanates. The last controller would only start running again if I checked the voltage in CONNECTION B.

Can one of you experts take a look at my diagram and specs and give me some guidance? Is there a chance that the problem lies with the used motor? Thank you.

Can one of you experts take a look at my diagram...
We can only if you post it...A bit more detail is also required, like what type is the motor? What is the speed controller?

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