Hello all, Phantom 3 standard- had a runaway and recovery some months ago.  Just got around to working on it.  Cleaned it up but could not get motors to spin. After trying everything I could come up with decided to replace the motherboard with a used one aparently of the same configuration.  After temporary connection of motors and everything back in place, I fired it up.  Had to reconnect the RC and updated the 8. (did not want to go too far with the update as I read of other issues with the latest)  Now I am at a point where there are no errors on the app and green LED's on the rear lights.  However the motors will not turn.  Not with the app or RC.  Still no error messages. Questions- could this motherboard be incompatable the motors? (These appear to be the newer motors).  Will the RC running 3.1.3 work with the older AC firmware?? Any thoughts or suggestions are appreciated.

Does other stuff work like calibrate IMU and gimbal?  Does the app say ready to go for ATI mode? I am assuming you have no GPS sats where it is located with the lid off like that.

How have you joined the wires between the motors and the main board? It looks as if you have twisted them together.

Sorry to read the issue. If you need any further assistance, please kindly start a case and send the unit in: https://www.dji.com/support

Everything seems to indicate no real problems/errors.  IMU and compass calibrate, GPS picks up the satellites just fine. Even gives me a takeoff notification when I use the auto takeoff on the app.  But no motor movement on any motor. Even get  green rear LED's.  As far as the twisted wire, yes I was hesitant to solder till I could confirm proper operation.   More thoughts?

Based on previous posts in the past, the motor wires need to be soldered directly to the board and not spliced, even soldered a t the splice joint. That said, you need to be sure the baord is a p3 board. The models P#3S, P34k, P3Adv and P3 pro all have similar looking boards.

Don't think older board with newer motors will work.

Any idea how to identify the model of the ESC?  The replacement board I bought looks, component wise, identical to the old board.  As far as the splices, I agree a non soldered motor is better than a splice but I see no way to do that with the existing motors.  I have seen other threads that have talked about splicing in the motors, again not ideal but seems doable.

on the ecs there is a model number

fans9e21fab5 Posted at 2018-3-22 04:48
Everything seems to indicate no real problems/errors.  IMU and compass calibrate, GPS picks up the satellites just fine. Even gives me a takeoff notification when I use the auto takeoff on the app.  But no motor movement on any motor. Even get  green rear LED's.  As far as the twisted wire, yes I was hesitant to solder till I could confirm proper operation.   More thoughts?

Have you tried to start the motors using the two joy sticks?  That would eliminate an app problem.

No joy with the joysticks either!! Even though the app shows takeoff, the motors are not spinning.  Wish there was a way to activate the motors individually to see if one of them has  gone bad.

fans9e21fab5 Posted at 2018-3-22 04:48
Everything seems to indicate no real problems/errors.  IMU and compass calibrate, GPS picks up the satellites just fine. Even gives me a takeoff notification when I use the auto takeoff on the app.  But no motor movement on any motor. Even get  green rear LED's.  As far as the twisted wire, yes I was hesitant to solder till I could confirm proper operation.   More thoughts?

The motor wires are coated in insulating varnish, before twisting them you need to scrape off all the varnish for a distance, then twist them together and solder them. It is a fair bet that one or more wires are not jhoined electrically, and that will stop the motors starting.

Thanks for the varnish info.  Will update when that is done.