I have a 2006 dodge stratus SXT. The heater when on turns to cold, then will warm up then goes cold and plays that little cycle. What could the issue be? Heater coil? I don't know.
Check your antifreeze level, if it isnt full, as well as the plastic reservoir, it will do the very thing you describe, also make sure radiator cap is on tightly. If you arent having any sweet smelling moisture issues in the interior, the heater core can be ruled out......
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