APM 2.6, one motor works while another similar one does not?

Hi all,
I’m having a little trouble getting a servo I recently purchased to work how I would like.
I originally bought a cheap smaller servo to test everything out with and had no problems at all, this was the Futaba S3003, which can be found here http://www.futaba-rc.com/servos/analog.html.
However now that I’ve purchased the larger motor that I will use, it behaves quite strangely and I’m not sure why.
This motor is the Savox SV-0236MG, which can be found here http://www.cmldistribution.co.uk/cml_product.php?productId=0000006204
When this motor is plugged in the serial LED flashes very quickly, stopping only momentarily for the blue light next to the PM port to flash, before the red light begins to flash repeatedly again.
While this happens the serial output is blank.

This is compared to when the Futaba is plugged in, when the output in the serial port is as it should be, and the serial LED only flashes every 2 seconds, which is the delay programmed into the loop.

I’m unsure if I’m missing a major difference between these two servos which is causing the different behaviours, but I’m having trouble finding this if there is.

Any input at all would be a great help and hugely appreciated.


Your servo probably draws too much current. You should power the APM via a power module and the servo rail via a separate BEC.

Thanks for the reply.
Yeah that would make a lot of sense. Thanks, I’ll look into it.

Don’t forget to pull the jumper when you power the rail separately!

This may be a silly question, but I’m unfamiliar with BECs.
The battery I’m using is 12V, would it not be possible to simply rewire two of the wires coming from the servo into the battery? Would a BEC still be necessary?
The motor is completely autonomous and requires no RC input.