AC Pressure, in 99 Escort

My compressor didn’t kick on the other day when i went to use my AC. The car is 10 years so i figured ok it’s time for a recharge. I hooked up my gauge and i put it on the low pressure side(you can’t out it on the high side because of the different connection sizes). It blew the gauge out! The psi was well over 100, and that’s the low side! Bought another one and the same thing happened.

My question is: Is the compressor blown? Or is there a pressure switch/regulator that regulates the two side (low/high psi)…Any ideas? AC knowledge is not my strong suit.

I’m going to have the system bleed and repair it myself either way.

Any advice is appreciated…

I could go into how the standing pressure of the system reflects the ambient temperature or how there is not a “bleed” procedure in AC repair or how you need to get a set of real AC pressure gagues but you are intent in proceeding your own way.

I was trying to gently nudge you into seeking a professional.

Without the compressor turning the pressures in the system equalize to a pressure dependent on the temperature of the entire system. Therefore, the low and high side pressures will be equal. If you are measuring the pressure with a warmed up engine both pressures can be high. You would have to reference the R134a temperature versus pressure table to find out what the correct pressure should be. Usually you get the compressor turning and then look at the low and high pressures as well as the sight glass. Usually a bad compressor will be physically noisy and/or the low side will have a higher pressure and the high side will have a lower pressure than specified for the ambient conditions.

The one reason HVAC techs charge so much for their work is that they have the tools and training to diagnose the system. Here is where diagnosis can help save the money of throwing parts at a problem.

Hope that helps.

Well umm thanks…Compressors not engaging, so any suggestions on what it could be then? I assumed that the AC system should be free of refrigerant before any work is done, like replacing the AC etc.

Thanks for the advice. I should take it to get diagnosed first i guess…

I don’t undertand why the gauge is blowing out. This is a full manifold gauge set with both high and low side gauges?

With the engine and A/C off and the system stabilized due to non-use the pressure reading should be the same on both high and low sides. With a properly charged system this means the reading SHOULD be over a 100 PSI. (normally around 115-120 PSI)

With the engine running and the A/C on (compressor engaged) and elevated RPMs around 1500ish or so, you should have around 30-35 PSI on the low side and 200-250 PSI on the high side. Those figures will vary by car and the conditions at the time. (ambient temp, humidity, car in the sun or shade, wind blowing, etc.)

If you’re using a full gauge set, do NOT open the high side valve when a can of refrigerant is tapped and opened into the gauge set. This could cause a can explosion which in turn could cause instant frostbitten fingers or permanent blindness if you’re hit in the eye with refrigerant.

Wow, thanx for the reply. That would ruin anyone’s day…I was tapping the low side only…I’ve come to the conclusion that I should take it in to get diagnosed. It’s probably better that way.

And yes it was over 100PSI on the low side so that makes sense, compressor not running and the car being cold. Never checked the high, but from what your saying it should be around the same number i got for the low. But for some reason the compressor wont engage with the AC turned on.