AC Blows Cold Only When Moving – Warm or Hot at Stops
DennisB WiseAutoTools.com © Summary: Air conditioning tips from an ASE Master Tech that has worked on car A/C in Florida for many years. When a vehicle’s AC system is not blowing cold, the first thing most people think of is adding some Freon. OK, but low refrigerant isn’t always the problem. If 134A is just added and the problem is NOT low refrigerant then now there’s an additional problem – an overcharged system. Read on to learn about the most common cause of a car or truck’s AC system not cooling while at stops and only cooling well while driving at highway speeds. If you have another AC issue, see our other AC articles for help determining the problem. Question – 2006 envoy A/C works fine while moving. Running at idle for few minutes starts blowing warm, not hot. Bought autozone cheap refill kit with gauge and saw that my system seems to be way over charged. Needle is half way into the red. Car was not running at the time. Is there a drain? Should car and ac be running? Need advice. Thank you
Answer – The AC should be running if adding refrigerant. The readings you see while the AC is not engaged are static readings. Working with refrigerant can be dangerous. No draining or venting of refrigerant into the atmosphere! Letting refrigerant loose into the atmosphere harms the Ozone and is illegal. Take the Autozone gauge back if possible, since it is practically worthless. High and low gauge readings from an AC Manifold Gauge Set, are needed to properly diagnose an AC system.
I’m not against DIYers working on their AC. That’s why I answer questions here in the comment sections of our Car AC repair articles and on our other blog, DenLor’s Auto Blog AC articles section. A little knowledge can be a dangerous thing though. With your specific problem, the system is not likely overcharged unless you overfilled it. If the AC works properly while you’re going down the road, the most likely cause of the AC not cooling while at a stop is the cooling fan not working as it should. Driving the vehicle allows plenty of air to be blown through the condenser (the AC component that’s in front of the radiator). While at stops the cooling (or condenser fan) is required to move the air cooling the condenser, So if the fan is not working, or if it’s too slow the air con will not cool the passenger compartment as it should.