I have a 1987 Grand Villa and the water temp gauge has started acting strange. At idle it jumps hot to cold and back very fast. I checked the water level and it was down, so I filled it, but the gauge strange movement is still acting up. As soon as I get up RPM and start driving it snaps right to 180 F like always.<br/>Any thoughts?<br/>Also where is the temp sending unit?<br/>Thanks