I crashed my old Phantom 2 standard old into the side of a building, but all of the electronics seem to be fully working. I read on a forum (https://phantompilots.com/threads/recycling-p2v-guts.103502/) that you cannot use the motors of a Phantom 2 with any other systems, or normal ESCs. To test this theory I plugged the motor into a standard ESC, and that into an Arduino. The motor did nothing, but sometimes broke free for a couple of seconds and started to spin, before clicking and reverting back to the original stillness. This seems like you could get the motors to work, but can you? Is it possible to get these motors to spin normally? Or is it like the forum said, impossible?

Not sure what you mean by "other systems."  What other systems do you want to use it with?  

When you crash a P2 and you subsequently have a motor problem such as you describe - where the motor starts and stops intermittently - there is either a problem with the ESC or a problem with the motor.  It's impossible to know which is bad for sure, but it's likely one is bad and the other is good.  My gut instinct in this crash is it's the ESC that's bad since you hit a building and likely forced a prop/motor to stop abrubtly which would often blow an ESC.  If you examine the ESC closely, you might see that it's blown.  Otherwise, you can't know for sure and there's no test to know for sure.  So you have no choice but to swap out known good motors or known good ESCs and then figure out what's good and what's bad via the process of elimination.  

As far as using P2 motors for different systems, you cannot use a P2 motor, that's a 2212, with a P3.  But you can use the 2312 motor with certain P3s but not others.  As far as the 2212, I believe they might work with the earlier Phantoms such as the original or the FC40.  But I'm sure the original Phantom and the FC40 have different ESCs.  It's complicated because the ESC is expecting to work with a given motor and the FC is expecting to work with a given ESC.  If it was me, I'd repair the P2.  I would stick with the Phantom 2 series when using this ESC and motor.  Be wary - don't mix the original P2 ESC and the advanced P2V+V3 motor - the 2312.

Good luck.

As for other systems, I mean making a DIY drone with a new flight controller, frame, and ESCs. Is that possible? I know that the ESC that I was using works, so does that mean that the motor is definitely broken? Also, I realized that in that forum they are using Phantom 2 V+, and I have a normal Phantom 2, did they change the motors between these two models? Because that would explain why I am getting some movement. Thanks!

I've never tried to build a drone from a aftermarket frame with P2 parts, so I don't know if it's possible.  I've rebuilt P2s though.  So if all the electronics are legit, I suppose it's possible.  If your ESC works perfectly, then that would seem to indicate the motor is bad.  The original P2V+ had the standard 2212 motors.  After a few months, the P2V+V3 came out which had a number of upgrades including the new 2312 motors which would eventually also be found on the early version P3 (not the P3S).  You can tell the difference by studying the structure/design of the motor at the top near where the vent is.  

"Getting some movement" meaning stopping and starting intermittently is what happens after a crash.  It means either the ESC or the motor is damaged.  It's very typical after a crash.  It has nothing to do with a mismatch of ESC and motor.  The reason you don't want to mismatch the ESC and motor is because the ESC could blow during flight without warning.  But that should never happen because you wouldn't mismatch the ESC and motor, right?  With a correct ESC and motor. the system is rock solid.  Until you crash.  You can mix and match any ESC with either of the two motors EXCEPT for the original ESC and the 2312 motor.  The original ESC, you could call it version 1.0, has no version printed on it.  The version 2.0 has V2.0 printed on the board.  The version 2.1 has V2.1 printed on the board.  Also some ESCs with no printed version had their FW upgraded in Shenzhen before they shipped but after they were manufactured, so they're good.  They are marked with a colored marker on top of the capacitor, not black.  This indicates the ESC FW has been upgraded.  Yellow, red, purple come to mind.  Any color other than black is good news.  The V2.1 ESC has a better chance of not blowing after a crash than the V2.0.  But they are both rock solid during flight.  Also, the original ESC will do low to high beeps and then four steady same key beeps after the start up.  The upgraded ESCs just do the normal low to high beeps without the four same key beeps.  

Hope this helps.  

Thanks, this is what I was looking for!