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Overcharge AC


My 2003 honda civic’s AC was not as cold as I thought it should be so I went to the auto parts store and bought a gauge and some 134a. Initalliy the gauge was at 39psi and in my heat (95F) the gauge I bought said it should between 45-55psi. After puting in a bottle and a half (18oz) of 134a, its still only at 42psi. Should I keep going or is my low pressure gauge broken? Thanks.

You have likely overcharged it. If you look under the hood, there should be a sticker that shows the capacity of the system. If it was cooling at all, it likely had more than half what is listed there onboard already, now plus the 18oz. you’ve added. At this point, the best thing you could do would be to bite the bullet and take it somewhere to be evacuated and properly recharged instead of guessing. You can destroy the compressor or blow out a seal if the system is overcharged. If it pops a seal when you’re working on it, you could suffer serious injury, not to mention an expensive repair.

There are a lot of factors that can cause a system to not cool properly besides being low on charge.
-The condenser fins could be dirty or the car’s fan(s) may not be coming on.
-A sensor or electrical control could be bad.
-The charge in the system may be contaminated with air or moisture.
-An internal fault could be present in the system.
-Your “blend door” may be not working properly, causing some warm air to mix with the cold.

Good luck

Two things, one are you taking the pressure with the AC on and running? Also Is the compressor engaging??

I don’t recall ever charging an AC system and seeing the low side pressure above 40psi when everything was operating correctly. With adequate air over the condenser fully charged systems operating at 1500 to 2000 rpm have always run 32 to 40 psi low side and 175 to 300psi high side depending on outside temperature. In the humid climate here it is easy to see when a system is charged by watching the condensation on the evaporator return line and accumulator.

Read this thread

You CAN NOT properly service an A/C system unless you are monitoring BOTH high and low pressure in the system…if you overcharge the system, the high side will respond first, with pressures quickly climbing way above normal…With the $20 recharge kits, you will be unaware of this and can easily damage yourself and your A/C system…If you INSIST on DIY A/C servicing, at least buy a SET of gauges so you can see what you are doing…

Thanks for the responses, I did charge with the AC on and the Compressor is engaging. I’m going to go get a high pressure gauge tomorrow but I don’t think I overcharged it…It’s blowing 55F in 95F weather.

55 degrees is right where you want to be in hot weather. It could still be overcharged. Did you look at the capacity? If so, what is it?

While there are really qualified people here on a/c, I think they should be smarter about responding. No one using a bottle from walmart is going to push the engine revs to 15 -20hun while filling the system. And since you arent there you have no idea on an overfill. There are other clues like short cycles. The blend door was a really good point. And yes 55 degrees is ok but you might still have blend door issues.

An experienced, seasoned tech can get your automotive a/c system within ounces of proper charge using nothing more than his eyes, ears, and fingertips. But those guys are getting harder and harder to find.

Get some gauges, tell us the readings. But also note for us whether the condenser fan(s) are running, ambient temp and humidity, whether the compressor cycles on and off quickly (10 sec or less) or less frequently, and what you see in the sight glass if your car is equipped with one at the receiver/drier.

Some of us just bungle our way through life, euryale1. But I didn’t recommend filling anything. I merely mentioned the normal pressures from a properly operating automotive AC when testing it PROPERLY with the PROPER equipment. But please feel free to point out any mistakes that I make in the future. I am always eager to learn from those more knowledgeable than myself.

I’ve got one of those and a full can of 134a. I’ve hooked it up a couple times but never trusted it and just had it serviced. I’m not sure what to do witht he full can just gathering dust. I’ve just decided the risks are just too high for me to work on the AC.