Replicator 2 extruder cooling fan stopped

Hi everyone,

The extruder cooling fan on my Replicator 2 completely stopped spinning recently. In an attempt to fix it, I ordered an identical replacement fan from MakerBot and soldered it in place of the old one. The fan spun when it was supposed to (i.e. any time the extruder was heated past 50 degrees Celsius), but it only spun very slowly/weakly, even as the extruder heated to the full 230 degrees. I tested it with a multimeter and found that the fan was receiving far less than 24V (I couldn't get a solid read on how much voltage it *was* receiving, but the readings peaked in the low single digits). After a few small test prints, the fan again stopped working entirely, and no longer spins at any time.

According to Google consensus, the most likely cause of this problem is a blown MOSFET on the motherboard. However, the closest problems to mine that I've seen don't mention anything about the fan spinning slowly first. Is a blown MOSFET capable of weakening a fan instead of stopping it outright? Are there any alternate possibilities besides the motherboard that I could check out before I pay $100 to get the motherboard replaced? I know it's not the EEPROM because, when the fan was spinning weakly, it correctly started to turn on at 50 degrees, and I know it's not overtightening of the bolts because the fan was still spinning just as weakly when it was outside of the extruder assembly.

Thank you!

When you tested with a multimeter did you test right on the board or were you testing the wire leads somewhere? I ask because I had an electrical issue once and it was driving me crazy. I swapped out parts by cutting two wires and wiring in a new part. That part didn't work either. Then I ran completely new wires and it did work. So, I inspected my old wires to find a cold solder joint under heat shrink. I would have never expected that. If you are getting less than 24v "on the board" then I'm thinking it's a board issue/failure.

I don't have a Replicator but can you go into the firmware and make adjustments like we who use RAMPS and Marlin can? If so, make sure that nothing got changed in the configuration files that controls the fan speeds on the headers.

If you are in the UK I have a tube of the transistors and will change it for you if it is faulty.