Go to the coolant temp sensor (at the thermostat housing) and clean the connector there. Then follow the wiring from that connector back up into the wire harness about a foot. There will be 2 bullet shaped connectors there. They are likely sort of green colored right now. Take them apart, clean them and swab them with some copper grease before you reassemble. You COULD have a bad regulator but you need to check pressure with a GAGE before you go replacing the regulator. Pressure at idle s/b @ 36 psi and about 40psi at say 3000 rpm.