My Dremel 4200 keeps stalling - anyone else?

Hey all, so I've had my Dremel 4200 for about a year now, mostly used for light sanding and engraving. Last week it started stalling under load, like when I press a bit harder on the workpiece. Battery is fully charged (checked with a multimeter, reads 20V). It'll run for a bit then just stop, and if I let it rest for a few minutes it starts up again. Anyone know what could cause this? TIA!

Could be the brushes. If they're worn out, they can lose contact at higher loads. Have you noticed any sparking around the commutator? Also, check if there's any debris stuck in the collet or gear housing. My old Dremel 3000 was like this right before the bearings gave out. Hopefully not that, but worth lubing the chuck and checking that the shaft spins freely.

I had a similar issue with my cordless rotary a while back. Turned out the battery was overheating. The tool would stop because the BMS circuit in the battery shuts it down to prevent damage. If the battery gets hot when it stalls, that's likely it. Let it cool down and see if it runs longer. Also, check if there's a reset button on the battery—some have them. If it keeps happening, might need a new battery.

Thanks for the replies! Dan, I did notice some sparking near the vents, so I'll look into the brushes. Sam, the battery does get warm, but not hot enough to burn. I'll check for a reset button, but I don't remember seeing one. Maybe I'll just take it apart (after unplugging, of course) and give the brushes a look. Also, I'm going to try using a different battery if I can borrow one from a friend to rule that out. Will update if I find the culprit!

If the brushes are sparking, that's likely the issue. They're easy to replace on most Dremels—there are little caps on the side. You can get a pack of replacement brushes for like $5 online. Also, make sure you don't run it at full speed constantly, that burns brushes faster. Hope it works out!