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Mark802
New User
Aug 19, 2026, 8:47 PM
Post #1 of 2
(1560 views)
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Should I keep Charging?
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The A/C in my ’91 Porsche 944 (3-liter engine, 117K miles) was working, but not very well, so I hooked up the gauges and saw that the static pressure was nearly the same on the low and high sides, so I thought I would add some R-134a. When I started charging, it was very hot in my garage, between 95-100°, and when the high side started to slide past 250 psi (low side read 35-40 psi), I decided to stop. The center vent temperature was 55°, so I figured that was probably as good as I could hope for. I drove the car the next day, and it got down to 40° on an increasingly warm morning. I had lunch with a friend for an hour, and now it was seriously hot outside, approaching 100°. The gauge in the center vent wouldn’t budge below 50° on the way home, and in fact, when I turned up the blower speed, it actually got hotter. Is this an indication that I should have kept charging the other day, even with the high-side pressure passing 250 psi?
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Hammer Time
Ultimate Carjunky
/ Moderator
Aug 20, 2026, 3:42 AM
Post #2 of 2
(1555 views)
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Re: Should I keep Charging?
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My advice is you should leave this thing alone before you destroy the entire system. Your knowledge of refrigeration is so far off I'm surprised it works at all.
System off, the static pressure is supposed to be equal and the pressure will only vary with outside temp.
It's normal for the duct temp to rise with the blower speed.
You cannot accurately charge a system by pressures.
You are supposed to completely evacuate the system and recharge with the exact specified weight of refrigerant. Only then can the pressures give you a picture of what is going on in the system.
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