I have a JD X520 that all of a sudden shut off with no electrical power. Main circuit 15A fuse was blown, replaced it & as soon as I turned the key, the fuse blew again. Happened a second time, checked wires for bare spots possibly shorting out, found nothing. Might it be the key switch shorting the circuit??
It might be the key switch, but they only go bad about 10 % of the times they get replaced for "going bad ".
Pull the plug off the back and test the switch .
There are tiny letters on the back.
G = Ground
B = Battery.
If the switch is bad those 2 terminals will have to be a direct short, but I doubt it.
PTO switches are the ones that go bad most often but again only about 1/2 the times that they are replaced for being broken.
In the on position power goes from the B terminal through the switch to the A or L terminal bringing the alternator into circuit and connecting the fuel shut off solenoid if fitted.
On some it also hooks the lights up to the AC feed off the alternator.
The shut off wire travels under the cooling duct and are prone to chaffing or melting.
Rectifiers go dead short more often than anything else.
The most usual cause of a dead short is the battery hooked up backwards.
JD wiring is a tad more complicated than most mowers and I strongly recommend buying the JD technical manual.
Written so a 10 year old can understand and use it, step by step instructions how to test the electronics and diagrams to show you exactly where every part is hidden and to top that off a "theory of opperation" section that tells you how everything works
