I just bought a 03 SUBURBAN 171,000 miles. Was driving it home and noticed it starting to overheat acting almost like the thermostat was sticking so I pulled over let it cool down so I could make it to the parts store. Once I turned it back on my voltage gauge is pegged out above 19 and my temp gauge is completely upside down, now at this point I don't know it that was what was going on so I replaced the thermostat anyways. So wasn't sure where to start with this. If anyone could give me advice I have a 500 mile drive tomorrow back home so I would love to have my temp gauge at the least fuctioning.