Anet A2 3D printer suddenly will not home X and Y I have been using my Anet A2 for about a year.  A few problems but none that I haven't been able to resolve. Today it suddenly stopped auto homing.

Using the position commands I can advance the X and Y positively but not negatively (after I manually re-position the carriages before turning the printer on).  Also the Y stepper motor makes an unusual noise and it will over advance the Y axis. This behavior was preceded by a feed fault. The print started fine but the stepper motor stopped feeding shortly after the print started.  

I am printing from an SD card as I always have. I changed SD cards thinking it might be a connection problem and I checked the G-code and all the commands including the E commands seem to be there. I have checked all the electrical connections - they seem to be fine.

Any suggestions to solve this?
I have experienced this a few times, usually this is related to the end stops.

If your end stops are somehow triggered (e.g. short circuit or cable broken; depending on the setup), the steppers will not home (as they think they are at the limits already) and only advance forward. Please look into the end stops of X and Y. Use a multi-meter to measure them and trigger them manually.

Alternatively hook up your printer to your computer with a USB cable and download a printer utility/application that can interact with the printer (e.g. Pronterface, Repetier-host, OctoPrint, etc.) and go to the terminal interface and send the M119 instruction to see the status of the end stops.