The water temperature gauge on my 69 charger is pegging to the maximum at warm idle. I just put in a new thermostat (180°F) and coolant and it is still reading high. I left the radiator cap off and watched the fluid in the tank from a cold start. The thermostat does not appear to open until the temperature gauge is pegged to the right. I checked the resistance from the temperature sending unit to the battery and the ground strap on the firewall at idle. I'm measuring ~23.5 ohms while the temperature gauge is pegged. The oil pressure gauge also appears to be pegged to the right, but the gas gauge is working ok. I checked the resistance from the battery to the engine, and from the battery to the firewall and got less than an ohm of resistance. I unplugged the bulkhead connector from the firewall and measured the resistance from the temperature sending unit plug to its pin on the firewall harness connector and got less than an ohm. The engine does not appear to be overheating. It does not leak out the radiator's overflow tube. What should I check next? Could the gas gauge be working if the dash's 5v voltage regulator was going out?
