Fan PWM problem

Hi,

I am using dual fans to cool PLA parts while printing. The fans are controlled by RAMPS. A single cable is plugged to RAMPS and I splitted it to two close to the fans. As you know some fans cannot be used on lower PWM values and my fans used to start rotating at 50-60%. Last week I was checking the wiring of one of the fans and somehow I flipped the connector and put it in wrong direction. I was expecting them to rotate in the inverse direction but instead the fan didn't rotate at all for a few seconds and then I've seen a very small explosion on the fan. I immediately shut the device down. I corrected the cabling, turned on again, and the fan started to rotate, the a small piece (like a very small rod) fell from the fan. I don't know what this piece is but somehow the fan still works without it. I didn't have a lot of problems for a week but now I can only activate the fan at full power (255) and it won't work at 254 or lower values. The funny thing is, the other fan is also behaving in a similar manner. Is it possible that I have damaged something on the RAMPS? Or should I change the problematic fan and try again? Do you have a recommendation for an easily PWMable fan?

Thanks

that little rod is the motor shaft, it is holding by pure magnetic field.

Yes replace the fan before it grounds itself and kill your board.

Hi,

Today I removed the fan to change it and that's when I remembered a modification I had made a while ago: I had soldered an electrolytic capacitor to the fan to enable rotation at lower PWM values. It had no effect at all on the PWM performance but explains why I had the explosion when I switched polarities. Also, that small rod like structure was in fact the capacitor's metal enclosure