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Slow A/C system refill

Hi everyone,

I just finished replacing my A/C system on a 1995 Camaro. New compressor, evap, condenser, etc. I’ve been careful to do everything right, and hooked up a vacuum pump & gauges to it today. I ran the pump for 45+ minutes, and then no issues as the system was holding vacuum a couple hours afterward.

But, when I then went to add the first 12oz can of refrigerant, the process was very slow. Took 20 minutes to get the whole can into the system. It did eventually all go in but that’s pretty slow, right? And I have another 20oz to go… Any ideas on what would cause this?

When recharging an automotive AC system, the engine must be at operating temperature, the engine idling at about 2,000 RPM’s, with a large fan blowing at the condenser.

Monitor the outlet duct temperature and gauge pressures.

You want to replicate the vehicle driving down the road.

Then you get nipples.


Disconnect the sensor on the accumulator and install a jumper into the harness connector. Doing so over rides the cycling clutch function. Just don’t allow the low side to go to vacuum and be certain that the jumper is disconnected and the harness reconnected before closing the hood.

Also, when charging into or behind the accumulator you can hold the freon can upside down and allow liquid to flow. The accumulator will prevent liquid from loading up in the compressor.

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Double check the system you installed is spec’ed for that much refrigerant. Modern AC systems use much less than those of earlier vintages. Adding too much can damage them.

your system was empty. Running compressor should draw in Freon quickly. If you have a restriction somewhere than you will have high head pressure and low flow to draw in Freon. I would bet on a restriction somewhere. Or you have a flaky fitting that is not allowing Freon to get into the system.

Thanks for the suggestions. I’m going to keep the condenser cool and occasionally increase the RPM and see if that helps.

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What I’ve done on slow fill A/C systems is to not only raise the RPMs a bit but I set the can of refrigerant in a pan of boiling or near boiling hot water., That will empty it much faster.

The sticker on my son’s 96 Camaro says 16 ozs of refrigerant. Seems low to me. And for what it’s worth I never charge a system by stated amounts. I always go by system pressures. Just my humble way of doing things. Hope som eof that helps.

Reading the FSM on my '79 Celica before I had the system evacuated and recharged the system, Toyota actually recommends putting the can of Freon in 120 degree water, as ok4450 suggests.
As it turned out, I had a leaky discharge hose, clogged TXV, AND a leak in the electrical prongs of the pressure switch, next to the TXV in the evaporator unit.

I got the job done (I hope…). Cooling down the condenser and revving to 2000 RPM at times helped some, but overall it was pretty slow going. I thought about using some warm water to help the cans getting so cold, but the big warning against “heating the can” kept me from trying it.

Thanks again everyone.

When they refer to heating the can they mean with the use of a torch or something like that. Boiling water even will not be a problem.
I think there are refrigerant can electric blankets which can be had and used to heat the can.

In my post, I referred to page 17-8 of Toyota’s 79 Celica FSM. They actually mentioned a max temp of 100F. (40C).
Being a newbie, and just getting my 609 certificate from Essco, I followed their advice.
AFter buying a gauge set ($50), vacuum pump($80), and leak detector($40), I would not recommend DIY A/C repair. But no one wanted to work on my car. It was “serviced” by a shop where the owner “topped off” the system with a can of “Freeze 12”, and worked for one season. I had a leaky discharge hose and clogged TXV. It’s running well for two seasons now.