Why Are Both the Upper and Lower Hoses Hot but the Fan Blows Cold Air?
2 Answers
Both the upper and lower hoses being hot but the fan blowing cold air is due to either a damaged water pump preventing water circulation or an internal blockage in the radiator. Damaged Water Pump: If the seal ring of the car radiator water pump is damaged, water will not circulate or circulation will be weakened. Lack of water circulation can cause the vehicle's radiator temperature to rise, potentially leading to engine overheating, and in severe cases, engine failure. Symptoms of a faulty car radiator water pump include coolant leakage near the engine's water pump area. Leaking coolant may leave traces of coolant color on the pump's ventilation holes, resulting in symptoms like high water temperature due to insufficient coolant. Additionally, unusual noises may come from the water pump while the engine is running. In such cases, it is necessary to visit a repair shop for servicing. Internal Radiator Blockage: Over time, without regular cleaning, scale from hot water continuously adheres to the radiator, leading to the accumulation of many impurities inside. When these impurities build up in one area, the pipes can become blocked. Simultaneously, some impurities in the water may clog the radiator pipe joints or filters, hindering smooth water circulation. Opening the valve to flush the radiator can resolve this issue.
Last time I drove, I also had an issue with the AC—the pipes were hot but the fan blew cold air, which was really annoying. The AC system works by circulating refrigerant; the high-pressure pipe should be hot while the low-pressure pipe should be cool. If both are hot, it could indicate insufficient refrigerant or a leak, causing a pressure imbalance in the system. If the small heater core is clogged with dust or rust, hot air can't enter the cabin, leaving only cold air blowing out. Another possibility is a faulty expansion valve or compressor malfunction. For a quick check, feel the temperature difference in the pipes, ensure the button settings are correct, and clean any dust from the condenser. Problems like this on hot days can make driving unbearable. I recommend not delaying and heading straight to a repair shop for diagnostics—it might just need a refrigerant top-up or clearing the small heater core.
