I've been having a Coolant Sensor problem on and off for a while having replaced the switch a number of times. The problem was at the Coolant Sensor connector. I removed both wires from the harness, cleaned both wire connectors with sandpaper but, most importantly, I used pliers to close both wire connectors so that the contact between the connectors and the Coolant Sensor was solid. I actually did away with the wiring harness which holds the two wires together. It was keeping one of the wires from making a solid connection (keep the brown wire with the white stripe on the passenger side - although I doubt it makes a difference. this is a simple switch). This worked like a charm (no more chimes!).