So when I bought the heep exactly 4 years ago, the A/C was blowing perfectly cold. Loved it. Over the next couple years is has progressively gotten warmer, and now to a point where I want to do something about it.
Today I bought a can of 134a with a guage on it; its one of those that has the dial which you set the 'ambient air temperature' and try to get the low line pressure to within a range. I hooked it up to what I am pretty sure is my low pressure line nozzle (on the V8 it is near the coolant reservoir, on the passenger side near the firewall, right?)
This is when I got scared. I hooked it up, car is running, A/C is full blast, compressor is on constantly (odd, because in the winter during defrost it is constantly kicking on and off every 10-15 seconds...). The pressure reads at 45psi. Perfectly within the 'acceptable' range. Then just for the hell of it, I turned the A/C, therefore the compressor, off. The guage jumps to somewhere around 125PSI!!!! That seems way too high, and it scared me too much to inject any freon into the system. Or really to do much of anything but run around the car to kill the ignition.
Is 125psi ok when the compressor is off?
Should I inject more refrigerant anyway?
What would you recommend doing to get my freezing air back?
Thanks a bunch!!!
I had a similar problem. It is best to use a manifold gauge rather than the one on the can. I filled the refrigerant to 35 PSI and it automatically rose to 50 and the compressor kicked on for the first time (Prob. in years) for about a second, and cycle on and off. When the compressor was on, it would go down to 20 PSI and kick off, and go back up to 50. I was worried sick because it was in the yellow on the can gauge, so I called Arctic Freeze and they said the gauge is supposed to be read when the compressor is on. The reason why it is going up so high on the gauge is because when the compressor is off, the whole system pressure (Hi and lo side) is equalizing, and the customer support person said it is supposed to go high. I would be careful, but if it is reading that high when your compressor is on, that is bad. It would be best to take it to a service center and have them fill it for the best results, though.
Dont worry about the pressures when the A/C compressor is off. The compressor may or may not cycle off when the engine is running, it probably will not cycle off with high outside temps and high blower speeds. It will more than likely cycle off more with the blower motor speed set low and/or with an increased idle speed though. You will generally want to see a low side pressure around 45PSI or lower depending on blower speed and idle speed. The compressor should cycle off around 25 +/- 5psi and cycle back on around 45 +/- 5psi. If the system is working good you should see vent temps down to or really under 50 degress (depending on outside temps, blower speed and idle speed) you should be real happy if you get vent temps in the lower 40's or even upper 30's
I tend to test maximum cooling potential of the A/C system with the A/C on recirculate mode, blower speed set on lowest setting and with or without an increased idle speed. I consider a good running system to be able to get below 40 degrees, but when its 100+ degrees outside this may not happen. When A/C systems can get below 50-55 degrees, thats almost not cold enough to stay comfortable in the heat of the day.
Is the a/c on recirculate while you're doing it? I've found that mine reliably doesn't cycle on recirculate if it has a full charge. I remember something from the Haynes manual about jumping the compressor while you're recharging it to get proper numbers.
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Here's the deal with your A/C compressor. It is kicking off due to low pressure. If you jump the low pressure switch to get the compressor to stay running please get freon in there fast, as you can burn it up. If you do not jump the low pressure switch but your compressor is kicking in and out constantly; just add a little more freon till it stays running. On the gauge that I use there is a mark at the very top of the green section. If yours is setup like that do NOT go past that mark. Too much freon can also cause your compressor to go bad. You have to find that fine line in between too much and too little. Also, use a thermometer in the vent. You should be getting pretty close to 50 degree F air blowing out of the vent.
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