I have a 2001 ZX2 with about 120,000 miles on it.
Recently, the temp. gauge on the dash has become possessed. It always starts at "cold", but then will quickly shoot up to the normal range, then go back to cold, then shoot up near "overheat" then drop back down and so on.
While this is happening, the heat coming out of the vents follows the gauge on the dash. That is to say, if the dash reads cold, the air is cold. If the dash reads hot, the air is hot. So the air coming out of my vents keeps switching from cold to hot and back to cold.
I recently had a problem with the gauge not working at all, and replaced both the temp sensor (inside the housing with the black hose), and the sensor that goes into the top side of the engine block. This fixed the problem for about 8 months, but now I am once again driving around with one eye on the gauge, hoping my car doesn't overheat.
Any help would be appreciated! Coolant levels are fine, and there are no leaks of any type on the car. Thanks!