1970 Chrysler 35 HP. Is it common for the horn to serve as the horn and over-heating alarm? Today, I discovered a bad/fried 6v horn in a 12v system. With the new 12v horn, the horn works and grounding the thermostat?s connection sounds the horn. When overheating the thermostat circuit works as a ground to the horn. I ran the engine 5 minutes (in the barrel) and the horn d/n sound. Plus, I could hold my hand on the engine?s cylinder area or head but I w/n want to leave it constantly over a minute or so. Does that sound about right for the combustion area surface temp?