Smell from DIY stir plate when I slow it down

[IDoBleedBrew]

So I put together my first DIY stir plate last night. Did the typical easy directions that you can find anywhere... 12 volt computer fan, potentiometer, 12 volt power supply, old HD enclosure.

Well it works fine when it is going full blast. It is a little noisy though and while the vortex isn't throwing the bar, it does make it rattle because it is constantly hitting the bar. I tried slowing it down some and that makes it much more quiet and brings the vortex down just to right above the bar, but then the thing starts stinking like burning electronics. Even if I just barely turn it down from full blast... it starts to smell. I turn it all the way up... no smell.

What might be causing that and what can be done (if anything) to correct it? Is it ok/safe to go ahead and run it at full blast?

 

[BitterSweetBrews]

Are you sure that the potentiometer is correct for 12v at the amperage supplied by your power supply?

 

[IDoBleedBrew]

Not really. How can you tell? Many instructions (and I've read dozens upon dozens) seem to make it sound like a 12VDC cell charger and a 2KΩ potentiometer simply work.

 

[IDoBleedBrew]

Well I don't know if it was the pot or how I had it wired. I swapped it out with another 2KΩ pot that came in the batch. This time I swapped the wire. I had the power in going to the middle prong and the power out on the left-most prong (if looking at it from the back). This had it reversed to where turning to the right slowed it down and turning to the left sped it up. This time I did power in to the middle prong and the power out on the right-most prong (if looking at it from the back) and it correctly slows it when turning the knob to the left and speeds it up when turning to the knob to the right. So far, I've been running it at not full blast for about 45 minutes and no weird burnt electronics smell. Not sure what was causing it that first time.