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What RPM'S should your car be at when ckecking your a/c with a manifold gauge?

I just bought an a/c manifold gauge set for testing my car’s a/c system. Should you test it with the the car at idle speed or should it be higher?

Working with a vehicle AC system can be very dangerous. From your question I assume you have no experience so I will offer this advice: Buy a repair manual and study it or have an experienced AC mechanic show you the basics. This is an area that you don’t want to tinker with without being safe.

When checking the rate of charge of an AC system, the engine should be idling between 1,800-2,000 RPM’s and a large fan should be pointed at the front of the vehicle. You’re trying to simulate the vehicle is being driven down the road.


Tester is correct of course and I’ll offer only one piece of advice since you’re new to A/C gauges.

NEVER open the high side valve on the gauge set when a can of refrigerant is tapped and the dispensing valve is open. This can cause a refrigerant can explosion which can cause frostbitten fingers in seconds or permanent blindness instantly if any refrigerant hits your eyes. Buy a pair of safety goggles anyway.