AC Refrigerant Charge Calculator

Determine proper refrigerant charge based on system specifications and ambient conditions.

Check underhood label or service manual for spec
Estimate based on cooling performance

R-134a Pressure Chart

Ambient TempLow SideHigh Side
70F / 21C25-35 PSI150-175 PSI
80F / 27C28-38 PSI175-210 PSI
85F / 29C30-40 PSI200-230 PSI
90F / 32C32-42 PSI225-260 PSI
100F / 38C35-45 PSI275-310 PSI
110F / 43C38-50 PSI325-360 PSI

Pressures measured with engine at 1500-2000 RPM, AC on max, recirculate.

AC Charging Guidelines

Proper Charging Procedure

  1. Recover existing refrigerant (EPA required)
  2. Vacuum system to remove air and moisture
  3. Check for leaks under vacuum
  4. Charge by weight using proper equipment
  5. Verify pressures match ambient temperature
  6. Check vent temperature (should be 35-50F)

Warning Signs

  • High low-side: Overcharge or poor compressor
  • Low high-side: Undercharge or expansion valve issue
  • Both high: Condenser blockage or overcharge
  • Both low: Low charge or compressor failure
  • Bubbles in sight glass: Low charge (if equipped)

Important: Never mix refrigerant types. R-12 systems require conversion before using R-134a. EPA Section 608 certification required for refrigerant handling.