Hey guys. I am at college in upstate NY and over the past few days I have been having a weird A/C issue. Here is the whole story: The air coming from the vents over the past week has been getting warmer and warmer (I was on the NYS Thruway for 3 hours on Sunday and there was little difference in temp between A/C on and A/C off with the same settings on the panel) until there is no difference in temp whether or not the A/C button is lit up. The compressor has been cycling on and off every couple seconds, so I felt that I had low refrigerant (AGAIN! I just recharged it first by me and then I had it checked out professionally less than a month ago!! It was working great with frostbite air.) I went to the WALMART across the street from campus and bought R-134a with Leak sealer and UV dye (with a hose, no gauge, white can) because I was assuming I had a hairline leak somewhere, but was not serious enough to cause a major problem.

I used a pressure gauge to check the pressure. The compressor was cycling on and off very quickly. It was not staying kicked in for long. What it has been doing is the pressure gets up to 45 PSI (FYI the temp during these tests was 63 degrees F according to the overhead thermometer with the A/C button lit, fan on MAX, temp on max cold (automatic system-notch below 66)), the compressor kicks in, the pressure drops fast to 25, the compressor shuts down, the pressure slowly rises to 45, the compressor kicks in, and it repeats.

I knew at that point that if the compressor was not staying on for long that it must be low on refrigerant (happened before). Refrigerant was about the only thing I can do with servicing an A/C system in the residence hall parking lot of a college campus. So, i proceeded to add the R-134a/dye/stop leak mixture. The compressor was now staying on for longer intervals and the pressure was falling at a slower rate. After adding like maybe 1/2 the can, I was getting some (not frostbite cold, but cold enough to tell the difference between A/C and fan) cold air back inside the car. The pressures remained the same even after adding the mixture. The only differences were the compressor cycle intervals and the low side pressure that controlled them.

Now here is where I almost went into a panic. After I turned off the A/C (button dark, fan on), the pressure slowly rose higher and higher until it finally rose to 65 PSI and froze there. On this gauge, that is the border to the RED DANGER ZONE. I stepped back in case something happened. I waited a few min and then went around to the driver seat to shut the engine down. I finally went back to check the gauge and it was frozen at around 62-65 or something like that. I found this weird that this was happening after adding not even a full 10.25 oz can of R-134a to an "almost-empty" system.

Also I let the stuff circulate for a long time and found no leaks that I can see.

NOW HERE ARE MY TECHNICAL QUESTIONS:

1. What is the low side pressure supposed to do? Cycle up and down like it is doing or stay at one pressure like 30-40 PSI?

2. Are the pressures supposed to climb toward and level off at a "danger zone" pressure when the A/C is commanded off or the engine is off?

3. Was I checking the pressure correctly or did I screw it up by doing things the nerd way?



Thanks.

BD


P.S. There are alot of Blazers and Jimmys here. There are AT LEAST 5 others parked in this lot alone, mostly 4 door 99+ models. One of my roommates even drives a 99 Blazer. I even parked next to a silver Blazer (same color as mine). I asked the owner how many miles he had just out of curiosity. He said 146k. I wonder if mine will be as lucky......

 

UPDATE: I went back out today and checked the pressure with the engine off and the temp at 74F. It was over 70 PSI. Dangerous?

When the A/C and engine are on, it just cycles between 25 and 45 or 50 like I said before. Does the cycling mean it is too high or too low on freon? Should I have it evacuated or add more?

 

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