Not powering fully on because fan will not spin,electical short?

Ok I only come here as a last resort and hopefully this question can help someone else. I've fixed a lot of Macbook Pros now and got one with a unique problem. It is not liquid damaged, but will not power on. I believe because somehow the fan will not turn on. The fan is NOT broken. The connector appears to not be broken, since I have a lot of spare Macbook Pro parts around so I have done the following:

resert smc and pram

reset smc and pram from external keyboard

tried to boot from cd

optical drive ejects and takes cd

turned on without battery

changed hard drive cable

changed screen ( in case data cable not being seated correctly was causing fan not to turn on)

changed to working fan

jumpstarted it

booted with different ram

booted without Ram

booted with one Ram in

hooked up to external screen

When I turn in on the Hard drive turns on, as well as the CD player, but no fan. Nothing will appear on the screen.It will actually stay on for quite a while and charges the battery. It seems like its not fully powering on because it needs the fan or it will turn off due to overheating. The screen and topcase are fine, I switched them both out and and am using a different logic board. I guess my question is, does someone know how to test if the fan connector has been shorted?