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Coolant recharge--compressor engages periodically

Eastplace on Mon June 06, 2011 10:53 PM User is offline

Year: 1999
Make: Chevy
Model: Astro
Engine Size: 4.3L V6
Refrigerant Type: R-134a
Ambient Temp: 100 F
Pressure Low: 45 psi
Country of Origin: United States

When my A/C didn't blow cold air at the start of the summer, I bought this recharge kit to see if I could save some money compared to taking it in to the shop:

I think that there was probably a leak in the system, so the leak sealant included in this kit's R-134a cans seemed like a promising alternative.

With the engine running, A/C on, and fan set to high, I connected the dispenser hose/gauge to the low side port. The reading of about 10 psi confirmed that the refrigerant was low. The compressor clutch wasn't engaging, though I figured that it was because of the low refrigerant pressure. I charged the system with refrigerant in small increments, aiming to get the pressure in the 50-55 psi range recommended for my ambient temperature. I had added about 1/3 of the 12 oz. can when I reached 45 psi. Then, the compressor clutch clicked on and the compressor engaged. Naturally, the low side pressure dropped, but it dropped to about 15 psi over 3-4 seconds. After that, the clutch switched off. With the compressor off, the low side pressure rose again--right back to 45 psi, over 5-6 seconds--and the cycle began again. Unsurprisingly, this cycle was not blowing cool air into the car. I let the cycle repeat around ten times before I shut off the engine.

The fact that the cycle itself is stable suggests to me that there aren't any fast leaks in the system. I wasn't able to detect any leaks with the U/V penlight provided either. So, am I right in the range of having enough refrigerant to trip the pressure sensor and engage the compressor, but too little refrigerant to sustain a low port pressure sufficient to keep the compressor from switching off? If so, then I can just add more of the can (I think I've only added ~4 oz. so far). Of course, I don't want to waste R-134a if it's a compressor problem, and I certainly don't want to let more into the atmosphere if there's a leak that hasn't already been sealed.

I've never worked with an A/C system before, so please pardon my ignorance. Thanks for your help!

JJM on Mon June 06, 2011 11:58 PM User is offline

Whatever you want to do is fine, really doesn't make a difference at this point. Chances are the entire system has been ruined by another "death kit". The only way to get a properly functioning system at this point is a TSR (Total System Replacement).

If the sealer is the type that just expands o-rings, you might be ok (but still significant service is required), but if it's true sealer, it's basically as if glue was poured into the system... I'll leave it to your imagination as to what's going to happen.


When considering your next auto A/C purchase, please consider the site that supports you:

Eastplace on Wed June 15, 2011 12:38 PM User is offline

Thanks for your assessment. I'm afraid you're probably right...and the cycle I'm getting would be consistent with there being at least one major constriction in the lines somewhere. I'll have a shop take a look at it.

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