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Last year the car started to blow the air a little warmer. I went to Walmart picked up one of those cans with the little gauges on it. The gauge said I was low so I filled it up. I had ice cold AC until this month. It started blowing hot again so I said I’ll just recharge it, the problem was when I bought the same can and put it on the gauge said that my system was overcharged. I went online and a lot of people were writing that you need a proper AC manifold gauges.

I got those today, plug them in and according to the paper it came with my system was low on refrigerant. I was about 30 PSI low side and high side was 200 PSI. The manual said for 83 deg. 40-50 on the low side and 175-200 on the high side.

Started to put the refrigerant out the low side started going down instead of up. So when I saw that I stopped filling it. I was at around 20 PSI on the low side and 210 on the high side. I revved the engine and then the low side went to 90 PSI and the high side came down to 125 PSI.

Any ideas what this could be?

2 Answers 2

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The expansion valve may have failed which would stop the refrigerant flowing around the system. The high side pressure would increase and the low side would drop due to a lack of supply back to the compressor.

When you revved the engine, either the low pressure sensor on the low side or the high pressure sensor on the high side will have tripped causing the compressor clutch to disengage which will cause the pressure to even out more, but because the expansion valve is closed the pressure may not be able to become totally even on both sides.

Since you said that it blows cold for a minute, then maybe the expansion valve is OK. It could be that there is moisture in the system. As the refrigerant expands in the expansion valve, moisture in the system can freeze and block the expansion valve, which could cause this issue. It may be worth getting the system professionally vacuumed out and a new drier fitted.

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  • I went to check if the compressor turns on and I noticed as soon as I turn on the AC it will blow cold air for about 1 minute and then the compressor starts to cycle on and off. It turns on for about 2 seconds and turns off and the car shakes. Then it does the same thing again until I turn of the AC or the car. If the compressor was bad would it still turn on and off?
    – RobNav
    Feb 25 at 23:12
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    To me, that sounds like the compressor is ok. One of the pressure sensors is turning it off, then when the pressure returns to normal it comes back on then repeats. I would say that the refrigerant is not circulating. I will add a little to my answer.
    – HandyHowie
    Feb 25 at 23:42
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The reading of 20 psi on the low side and 210 psi on the high side would indicate a restriction somewhere in your ac system. A clogged orifice or expansion valve is a common cause. The high-side pressure may be elevated as the compressor attempts to force the refrigerant past the obstruction. This will quickly starve oil flow to the compressor and cause it to fail.

Revving the engine and having the low side jump to 90 psi and high side drop to 125 psi would indicate a weak or failing compressor.

You have a leak in your ac system. Your best bet is to fix that first and then evacuate and recharge your ac system.

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