ASE G1 Auto Maintenance and Light RepairHeating and Air Conditioning (HVAC)Easy
A technician is evacuating an R-1234yf system. What color hose is universally designated for the low-side service port connection on manifold gauges for this refrigerant type?
- AGreen
- BRed
- CBlue
- DYellow
Show answer & explanationAnswer & explanation
Correct answer: C. Blue
In automotive AC systems, the blue hose is universally designated for the low-side service port, regardless of refrigerant type (R-134a or R-1234yf).
Why the other options are wrong
- A. Green is sometimes used for specific hybrid vehicle AC systems or for nitrogen, but not universally for the low-side port.
- B. Red is for the high-side service port.
- D. Yellow is for the vacuum pump or refrigerant tank connection.
Manifold Gauge Hose Colors
Standard color coding for automotive AC manifold gauge hoses: Blue for low-side, Red for high-side, Yellow for vacuum/charge port.
- Blue = Low-side service port.
- Red = High-side service port.
- Yellow = Center port (vacuum pump/refrigerant source).
- Prevents cross-contamination and incorrect connections.
Memory trick: Red is hot, Blue is cool, Yellow fills the tool.