MakerBot: Common issues

Here is a list of possible issues that you can run into and tips and tricks on how to fix them.

The heater starts building temp, but then it drops off

FET overheating

(Problem) Description when the heater is started the heat starts to rise but after a while it stops building and drops back to around the ambient temperature.
While the heat is rising the led on the extruder board labeled LED5 is lit, but after the temp starts to drop it is no longer showing any light.
The FET (the component might be labeled "RMX 5003") between the LED5 and LED6 is warm to the touch when the led is lit. After this the temp won't build at all.

• If the FET has overheated and it is the protected sort then disconnection the extruder and reconnecting it will reset the safety function.
• If the FET has overheated and it is not the protected sort then it probably fried and needs to be replaced.

Missing solution here