What Causes High Water Temperature When Idling with AC On?
3 Answers
If the water temperature remains normal during driving and when the AC is off, but rises only when idling with the AC on, it indicates a malfunction in the cooling fan of the AC evaporator, which requires inspection and repair. Here are solutions for high water temperature when idling with AC on: 1. Cleaning: Visit a professional repair shop or 4S store to clean the condenser, radiator, and inspect the fan and cooling fins. 2. Rinsing: When washing the car, you can appropriately rinse these components with a hose. 3. AC Usage: Turn on the internal circulation when using the AC to save costs, maintain lower cabin temperature, and avoid waste. 4. Cooling Method: Use intermittent cooling; after the cabin temperature drops, you can turn off the AC and turn it back on after a while.
I've encountered this situation several times, especially in summer when idling with AC on while waiting in the car. The coolant temperature gauge keeps climbing rapidly. The main reasons are: insufficient engine cooling at idle speed with slow fan rotation failing to dissipate heat effectively; simultaneously, AC compressor operation significantly increases engine load, resulting in poor combustion efficiency and more heat generation. Additionally, factors like clogged radiator, accumulated debris blocking front air vents, insufficient or contaminated coolant with poor circulation can all prevent proper radiator cooling. Last time I checked, the fan wasn't even spinning - possibly due to a faulty relay. Immediate action recommended: turn off AC, open windows for ventilation, and avoid idling with AC on for over 10 minutes. Regular maintenance including coolant checks and radiator cleaning can prevent major troubles.
This is a common issue during car repairs where customers complain about the water temperature skyrocketing when the AC is on while idling. The engine's thermal efficiency is low at idle, and the slow air circulation makes heat dissipation difficult. Turning on the AC increases the engine load by about 30%, causing heat to build up even faster. The cooling system can't keep up: the fan belt might be loose, reducing rotation speed; the radiator or cooling fins could be clogged, impairing airflow; or the coolant may have degraded, reducing its heat absorption. A simple DIY check is to see if the fan is running when the temperature rises. If not, turning off the engine to let it cool down helps. Regular maintenance of the fan, thermostat, and cleaning can prevent many such issues.
