Chrysler Repair: sebring heating problem, warm weather, filler cap

Question
sir;   My sister-in-law has a sebring and has  heating problems #1 in the summer it will over heat at low speeds or idleing unless you wire the fan to run all the time...#2 In the fall and winter it has no heater...RM..

Answer
Hi Randall,
That sounds like a problem with circulation of the coolant in the system. Has the system ever been cleaned and flushed? If not, that would be the first thing to try. Then if that doesn't improve things, the water pump's circulation might be compromised, which can be assessed by looking in the filler cap with the engine running but not yet fully heated to see if the coolant appears to be moving. You would want the gauge to be reading above the cool level but not so hot as to be pressurized, for reasons of avoiding steam blow off.
Where does the gauge read in cold weather? If it reads low on the scale then the thermostat may be stuck open which prevents the coolant from getting warm enough to produce any heat. But then in warm weather the system would not overheat unless the radiator were partially restricted in its flow, so that is a dilemma. But things can change over the months.
So consider those ideas and let me know the answer to the questions I listed.
Roland