Ok, if you reverse the wiring and the bendix engages the flywheel, this means it is NOW wired correctly. The bendix will not disengage the flywheel until the engine starts. If the starter motor spins, but does not turn the flywheel, this would indicate a bad bendix. If the starter motor does not spin, then you need to check voltage at the starter motor with the key in the start position. If the voltage is below 10 V I would then have the battery load tested, as you may have a bad cell in the battery.