Contour Enthusiasts Group Archives Forums General Troubleshooting A/C charge too high??

My AC hasn't worked in a few years so some details might be sketchy. Anyway, years ago it was short cycling and took a long time to start cooling (like 10+ minutes) so I started with the obvious of checking and recharging the refrigerant. I think at the time it read low, then I started charging and it quickly went to high, up to the red zone. I stopped charging thinking it's dangerously high and lived with the short cycling for a while. The next year I replaced the pressure cycling switch before summer thinking that would solve it, but compressor didn't engage at all, nothing came on. I thought it was compressor clutch or something costly so I didn't pursue it. Years go by...

Today I thought, what the hell, I'm going to recharge it with the half can of leftover R134a. To my surprise, it started cycling again, though a short cycle. But my problem is this: the gauge would read very high, in the red zone, then a hiss comes from the compressor area, the pressure would dip quickly all the way down to the lowest (green) zone. Then pressure then builds back up to red, hisses, and drops to low again. I'm out of refrigerant now but I want to know if the pressure is high or low. The high reading scares me, but then it dips down so I don't really know if it's high or low. I don't know the extent of the leak so at the very least I want to be able to fill it full and evaluate if/how long the AC will work. Assuming there is no refrigerant, how many ounces would I need?

what did the gage exactly read? what was the high side pressure? did you liquid or gas charge the system? sound like you where liquid charging and that will cause the low side pressure to jump very high


the end of it all is if the system wasn't turning on at all the system was empty or over filled. either way you can't fill the system correctly unless you have a vacuum pump. you can't just dump R-134A into the system, you need to get the air out as it reduces the efficiency of the R-134A

also if you heard a hissing the leak might be so bad that this is what you heard


what you need to do is take it to a shop if you don't have the right tools to work on the A/C system

you need to first determine the high and low side pressures to see if it needs to be refilled or if it is leaking and fix that first, vacuum down the system and make sure it holds the vacuum and then recharge to correct levels for R-134A and oil ...



edit: almost forgot, you do realize that the pressures the system sees changes depending on the ambient temp right? if you are in one of these areas seeing 100 degrees the high low side pressure might be right ...

i have the exact same problem...i'd love to know what to do.

Man, that's quick response. The high reading was 60-70. The low is <20. What does that mean exactly, that the low reading is correct or the high reading is? The refrigerant did go in as the can is empty now. But I see your point about air being in the system, not that it won't charge. I'm assuming I was liquid charging as I had to shake the can before using.

Bummer about maybe having to take it to a shop. More time and more money than I care to spend, that is why I haven't done it all these years and just lived with the heat.

did the low reading continue to go up as you filled it. i.e. if it started at 60/15 did it end up being 60/20 after a while.

When i filled mine a couple year ago when the compressor was cycling it was reading high and low, but when I put enough in for the compressor to actually stay on, it was the lower reading that was staying.

Well I only had half a can (or less) so now I'm out. I don't think enough got in there to make a difference. Either that or the leak is so bad the charge is not staying. That's why I was hoping someone could tell me whether I should be buying 2+ cans and dump it in or it's already overcharged and my problem is elsewhere...

Attempting to charge an A/C system with only a low side guage is like trying to perform brain surgery with one eye covered - NO DEPTH PERCEPTION.

If you're trying to do so, forget it and go get a set of manifold guages so you have the proper perspective on what the system is doing.

When looking at only the low side, it is common for:

1) static pressure to be upwards of 100 psi when the compressor clutch is not engaged,

2) readings of 60 psi and greater when the valve to the can is open (you're reading the can's pressure, not the system)

3) under or over charge the sytem since it is virtually imposible to guage the state of the system's charge based solely on the low side reading.

Steve