extruder motor stopping after a while

Hi everyone,
I just ran into a problem with my new Mendel. When I turn it on and start printing I can see the filament going down and making the first 2-3 layers. After that, the motor feeding the PLA stops working and I have to stop the print.
If I touch it, it's a bit hot so I think it stops for this reason (a bit hotter than the other motors)
If I use pronterface and ask it to extrude, say, 2mm, the motor starts vibrating a bit and then stops, but it doesn't move. If I try to move the motor gear with my hands, it still works.
If I do the same when the printer is just turned on, everything goes fine.
Using nophead's Mendel90 model, green PLA.

Any hint?

Thanks in advance

If the motor is a lot hotter than the others is seems the current is set too high but that would be odd because the Melzi's are all set to 1.2A when we send them out. Have you changed the current setting? Do all the presets look to be set to the same position? If you have a meter turn the motors off and measure the reference voltage on the presets. They should all be about 0.5v.

The extruder motor will be a bit hotter simply because it it sits over the bed and the hot end. The other possibility is a bad connection that gets disturbed when the carriage is moving. Try extruding in pronterface and then move the ribbon cable to see if it intermittent.

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[www.hydraraptor.blogspot.com]

Hi,
thanks for helping but it seems another kind of problem. No change to any settings anyway, and strange that it stopped working while printing.
Anyway I disassembled the whole X Axis group and found that even pushing or pulling with hands has no effect, so the motor couldn't work. The filament is blocked into the peek nozzle holder (even with hotend at 220°C). The motor tried to force but at some time the little screw blocking the gear has unscrewed a bit, so the motor works fine but the gear slipped and couldn't move anymore.

Now I have to find a way to free the nozzle....