How to Solve the Problem of Hard Brakes When the Air Conditioner is On?
2 Answers
When the air conditioner is on, the brakes feel hard because the air conditioning reduces the vacuum assist for braking, making the brake pedal harder to press. The increased engine load and reduced throttle vacuum lead to a decrease in braking vacuum power, but the impact should not be significant. If the brake pedal cannot be pressed down, there may be an issue with the brake vacuum system. In such cases, the vehicle should be taken to a 4S shop for repair as soon as possible.
I've been driving for over a decade, and it's quite common for the brakes to feel harder when the AC is on. Mainly because the AC compressor kicks in and steals engine power, causing the vacuum booster pump to spin insufficiently—simply put, the brake assist weakens. Especially when idling at a red light in an automatic transmission car, you can clearly feel the brake pedal getting progressively stiffer, sometimes requiring extra effort to keep the car stationary. Don't panic in such situations—the simplest fix is to immediately shift to neutral and lightly tap the gas pedal to raise the engine RPM, which should resolve the issue right away. Regularly check the vacuum hose for cracks every 5,000 km, as older cars are particularly prone to vacuum leaks. If the whole car shakes when braking with the AC on, there's a good chance the one-way valve inside the vacuum booster reservoir is faulty—get it replaced ASAP! Safety is no trivial matter!
