In our heavy snowfall a couple days back, i went out to start my 1989 chevy k-1500 plow truck to plow the driveway.it started fine but had low voltage,when i put it in four wheel drive it worked for about 25ft then quit,the lever is still engaged but four wheel drive is not working,it starts and runs great,but it just doesnt engage into 4x4 and takes all the amps from batt just to lift plow,i am thinking there are several issues going on here. Can anyone help?