A/C Pressure Chart
R-134a & R-1234yf
Expected low- and high-side pressures for the temperature you’re actually working in — then read your gauges against them. Enter a ZIP and we pull today’s ambient for you.
Reference chart
A/C pressure chart: R-134a and R-1234yf by ambient temperature
Expected low-side and high-side gauge pressures for a healthy, running system, from 60°F to 110°F ambient in 5°F steps. The expected window moves with ambient temperature, so find the row for the temperature you are working in and compare your gauges to it.
Orifice-tube and expansion-valve (TXV) systems run slightly different windows, so each refrigerant shows both. Across this chart, R-1234yf windows sit within 5 psi of R-134a at the same temperature and system type. Outside 60–110°F the chart does not list pressures.
What should A/C pressure be at 80°F?
- R-134a, orifice tube: low 38–48 psi, high 185–225 psi
- R-134a, expansion valve: low 35–45 psi, high 180–220 psi
- R-1234yf, orifice tube: low 39–49 psi, high 190–230 psi
- R-1234yf, expansion valve: low 36–46 psi, high 185–225 psi
R-134a
psi gauge| Ambient°F | LowOrifice | LowTXV | HighOrifice | HighTXV |
|---|---|---|---|---|
| 60° | 25–35 | 22–32 | 110–150 | 105–145 |
| 65° | 27–37 | 25–35 | 130–170 | 125–165 |
| 70° | 30–40 | 28–38 | 145–180 | 140–175 |
| 75° | 32–42 | 30–40 | 165–200 | 160–195 |
| 80° | 38–48 | 35–45 | 185–225 | 180–220 |
| 85° | 42–52 | 40–50 | 210–250 | 205–245 |
| 90° | 45–55 | 43–53 | 230–275 | 225–270 |
| 95° | 48–58 | 45–55 | 250–300 | 245–295 |
| 100° | 50–60 | 48–58 | 270–325 | 265–320 |
| 105° | 52–62 | 50–60 | 290–350 | 285–345 |
| 110° | 55–65 | 52–62 | 305–365 | 300–360 |
R-1234yf
psi gauge| Ambient°F | LowOrifice | LowTXV | HighOrifice | HighTXV |
|---|---|---|---|---|
| 60° | 26–36 | 23–33 | 115–155 | 110–150 |
| 65° | 28–38 | 26–36 | 135–175 | 130–170 |
| 70° | 31–41 | 29–39 | 150–185 | 145–180 |
| 75° | 33–43 | 31–41 | 170–205 | 165–200 |
| 80° | 39–49 | 36–46 | 190–230 | 185–225 |
| 85° | 43–53 | 41–51 | 215–255 | 210–250 |
| 90° | 46–56 | 44–54 | 235–280 | 230–275 |
| 95° | 49–59 | 46–56 | 255–305 | 250–300 |
| 100° | 51–61 | 49–59 | 275–330 | 270–325 |
| 105° | 53–63 | 51–61 | 295–355 | 290–350 |
| 110° | 56–66 | 53–63 | 310–370 | 305–365 |
Orifice = fixed orifice tube system · TXV = thermal expansion valve system · ranges are min–max psi on a running system
Test conditionsThese ranges assume a RUNNING system: compressor engaged, engine held at 1500-2000 RPM (NOT curb idle — idle reads 30-60 PSI low on the high side), blower on high, doors open, ~2 minutes stabilized.
Source: Robinair RG3 + MACS automotive A/C training-chart consensus. Indicative for healthy systems — cross-check against the vehicle manufacturer service spec for the exact make/model before condemning a part.
refrigerant-pressure@1.0.0REFERENCE DATA — NOT A MEASUREMENT
Between two rows, or want your own reading checked? Use the lookup below: it takes your ZIP or shop temperature, interpolates the window for that exact temperature and tells you what your gauge pattern points to.
What each gauge pattern means
Run a lookup above and the six gauge patterns — and what each one points to — appear here.
Frequently asked questions
Why does it ask for my ZIP code?
A/C pressures move sharply with outside temperature — the same healthy system reads very differently at 70°F and 100°F. Your ZIP lets us pull today’s actual temperature and humidity so the expected window matches the day you are working. Working indoors, or the bay runs hotter than outside? Switch to “Enter shop temp”.
Does the system need to be running?
Yes, and this is where most bad readings come from. These ranges assume the compressor is engaged, the engine is held at 1500–2000 RPM (not curb idle — idle reads 30–60 PSI low on the high side), blower on high, doors open, and about two minutes to stabilize. A system that is off reads about the same on both sides, and that reading rises and falls with the outside temperature; that is not a fault.
Orifice tube or expansion valve — how do I tell?
Follow the liquid line from the condenser. An orifice tube system has a fixed restriction in the line itself and an accumulator on the suction side near the firewall. A TXV system has a valve at the evaporator inlet and a receiver-drier on the high side. Most GM trucks are orifice; most imports are TXV.
What about R-12 or R-22?
Neither is charted here. R-12 was banned for new automotive use in 1995 and most of those vehicles were retrofitted, so confirm what is actually in the system from the service-port fittings and any retrofit label before charging anything.
Can I condemn a compressor from these numbers?
No. This is reference data — a consensus of Robinair RG3 and MACS training charts — not a measurement of your vehicle. Use it to decide where to look next, then cross-check the manufacturer service spec for that exact make and model before replacing a part.
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