overheats. so I changed fan relays . and now rough idle with ac on. with ac blown hot air while not driving with ac compressor engaging on and oft for seconds . when I drive it becomes good ac .
My car has 50000 miles.
My car has an automatic transmission.
When the a/c is on, the engine is more heavily loaded because the engine has to drive the a/c compressor. If the engine is not in optimum condition, that extra load may cause a rough idle. The underlying causes of rough operation under load could be a bad tank of gasoline, dirty fuel injectors, incorrect idle speed, exhaust restrictions, vacuum leaks, incorrectly installed or damaged spark plugs, a defective or clogged fuel pump or fuel filter, failing electrical components such as the ignition control module, plug wires, coils, and spark plugs, a defective airflow sensor, dirty oxygen sensors and other causes. The a/c "idle up" function should also be checked. I would recommend that you request a rough operation/rough idle diagnostic and the responding certified mechanic will perform the required diagnostic steps to get this aspect of your inquiry resolved.
With regard to the a/c system blowing air that is not cold enough when you are stopped, when your car is moving there is lots of air flow over the condenser (the heat exchanger in front of the radiator) and that airflow is essential to proper a/c system operation. To maintain good airflow when the car is in stop and go traffic, or is completely stopped, condenser fans will come on automatically. If the fans do not come on, the circumstance you have described could occur. However, what you have described could also be due to a low state of refrigerant charge. Other possibilities are that the compressor clutch is not cycling as intended or that the condenser might be blocked or dirty. And, of course, you could have a combination of these issues. To get the a/c issue resolved, the best thing to do is request an air conditioning system inspection. The responding certified mechanic will come to your location, pinpoint the fault and get this resolved for you. Once diagnosed, the mechanic will be in a position to give you a repair strategy to get the A/C system fully functioning and he or she will estimate the cost of the required repair. If you have further questions or concerns about either repair service (rough idle and a/c problem), do not hesitate to re-contact YourMechanic as we are always here to help you.
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