so I went too push snow last night and went to turn the lights on and there was a screeching noise from the belt and the lights would only work for about ten seconds and the dim out. my first thought that the alternator is bad but just seem odd that nothing else make it do that, cab heater runs fine incab light dose fine just the headlights and rear lights. any ideas before I spend money on an alternator?
I'm not familiar with the exact setup of the 257 but my 248 would allow rain or melting snow to run into the alternator and freeze it solid in cold weather. Have you checked that the belt hasn't burned through? It only takes a minute for that to happen. If you find the alternator frozen and can't move the machine inside use a hair dryer or heat gun to warm it and see if it will free up. Otherwise test with a volt meter off the output lug on the alternator to determine if it's charging, it should ideally read 13.8 volts but should be more than 12 at minimum.