Does idling with the air conditioning on harm a diesel vehicle?
3 Answers
Idling with the air conditioning on can indeed harm a diesel vehicle. The following are the hazards of idling with the AC on: Reduced battery lifespan: In principle, the air conditioning compressor is driven by the engine, while the blower fan is powered by the battery. During idling, the vehicle may not necessarily charge the battery. Excessive power consumption by the blower fan can lead to battery depletion, thereby affecting the battery's lifespan. Carbon buildup: Keeping the AC on while idling requires continuous engine operation. Prolonged idling can also impact the engine. When idling for extended periods, the gasoline entering the combustion chamber may not burn completely. Incomplete combustion produces large amounts of carbon monoxide, and some carbon deposits may accumulate. Since the airflow into the engine during idling is low, the flushing effect on carbon deposits is minimal. This increases the risk of carbon buildup in the engine.
As a driver who has operated diesel trucks for over a decade, I can tell you that prolonged idling with AC on does harm the engine. I remember waiting at a highway rest area during a delivery run – I slept for two hours with AC running, and later clearly noticed increased carbon buildup in the exhaust pipe along with higher fuel consumption. This mainly happens because diesel engines don't achieve complete combustion at low RPM, and with insufficient exhaust temperatures, the injectors tend to develop coking deposits over time. We long-haul drivers all follow one principle: if parked for over 15 minutes, it's best to shut off the engine. If you must run AC, restart the engine every half hour for ten minutes to let the vehicle 'catch its breath' – otherwise the exhaust treatment system gets clogged easily.
Last week, I repaired a diesel SUV with a clogged DPF. The owner had been idling with the AC on during daily lunch breaks. The biggest risk of idling with AC in diesel vehicles is particulate filter blockage. You see, at idle, the engine temperature is only 70°C, while the DPF requires over 250°C to burn off carbon particles. When we opened it up, the filter was completely caked with black soot. Just cleaning the DPF cost the owner over 2,000 yuan. My advice to diesel vehicle owners: When using AC, it's best to switch to sport mode to increase RPM, or rev the engine to 2,000 RPM every 20 minutes - white smoke from the exhaust means regeneration is occurring.
