Automotive A/C Hose by the Meter: How to Choose the Right Air Conditioning Hose

If you service truck, bus, construction-machinery or refrigerated-unit air conditioning systems, buying A/C hose by the meter is usually far cheaper than stocking finished assemblies. You cut what you need, crimp the fittings, and keep one reel on the shelf instead of fifty part numbers.

The problem: not every “rubber hose that fits” survives a refrigerant circuit. Permeation, temperature and burst pressure decide whether the hose lasts five years or five months. This guide walks through the four decisions that actually matter, with real series data rather than generic advice.

1. Start with the refrigerant, not the hose

Refrigerant molecules are small, and R1234yf in particular will migrate straight through a non-barrier tube. That is why modern A/C hose is built with a polyamide (PA) barrier lining inside the rubber tube:

• R134a / R1234yf car and truck systems — barrier hose is standard practice; the CA5, CA9 and EA4 series are built for these refrigerants.
• R404a / R410a transport refrigeration — larger molecules but higher operating temperature; the EA48 series is permeation-tested with R404a / R410a at +80°C at max. 9.7 kg/m²/y.
• R12 legacy systems — ask before ordering; hose compatibility is not interchangeable.

If your customer’s unit is a refrigerated box on a truck, do not sell them a car-series hose. The temperature rating is the giveaway: EA4 runs −40°C to +125°C (max. +150°C), while EA48 is rated to +140°C and heat-aged at +140°C × 200 h.

2. Four layers or five? Thin wall or thick wall?

The layer count is not marketing. Reading from the outside in, a modern A/C hose is:

1. EPDM cover — weather, ozone and oil resistant
2. PET braid reinforcement — carries the pressure
3. EPDM inner tube — oil and temperature resistant
4. PA barrier lining — stops refrigerant permeation

4-layer (EA4) is the light, flexible, easy-to-crimp option for standard engine bays. 5-layer (CA5) adds a further EPDM layer for extra permeation resistance at the same 3.5 MPa working pressure. Thick-wall 5-layer (CA9) is the heavy-duty choice: at CA9-080 the wall is 5.4 mm against 3.5 mm on an equivalent thin-wall hose, and weight goes from 141 g/m to 285 g/m — worth it where the hose rubs against a frame or sits next to a hot manifold.

3. Sizes: #8, #10, #12 and what they mean in millimetres

Workshops talk in dash sizes, factories talk in millimetres. The practical conversion used across our series:

Table: selected sizes from the production series. Full size charts (all 20 part numbers) are on each product page.

• #8 ≈ 8.2 mm I.D. (suction line on many truck systems)
• #10 ≈ 10.2–10.7 mm I.D.
• #12 ≈ 12.7 mm I.D.
• #16 and above (16.1 / 18.5 / 22.2 mm) — large discharge and refrigerated-unit lines

Always size by inside diameter against the fitting, then check the minimum bend radius (55 mm on an 8 mm hose, up to 135 mm on a 22 mm hose). Forcing a hose below its bend radius is the single most common cause of premature failure we see in returned assemblies.

4. What the pressure numbers actually mean

Every series above is rated 3.5 MPa working pressure with a minimum burst of 18.0 MPa — roughly a 5× safety factor, which is what SAE J2064 expects. When you compare suppliers, ask for the test record, not the catalogue number:

• Burst test: measured 35 MPa on our EA4 series inspection (SAE J2064 requires min. 13.7 MPa)
• Proof test: 7.0 MPa hold, no leakage or abnormality
• Length change at 3.0 MPa: within +2% to −4% (measured 0%)
• Wall eccentricity: 0.15–0.33 mm measured against a 0.4 mm limit

A hose that swells under pressure changes its length, pulls on the crimp, and eventually weeps at the fitting — which is why the length-change figure matters more than most buyers realise.

Buying by the meter: what to expect

• MOQ: 100 meters per size
• Stock: common sizes are held in stock
• Lead time: 3–7 days after order confirmation for stocked sizes
• Crimping: standard A/C crimp machines and dies work on these series; matched aluminum fittings are available
• Finished assemblies: if you would rather not crimp in-house, assemblies can be built to your drawing, sample or OE number and are 100% pressure / leakage tested before packing

Need a hand selecting?

Send us the refrigerant, the I.D. you need, the operating temperature and whether the run is suction or discharge — we will tell you which series fits and quote within 12 hours. Relevant product pages:

• EA4 4-layer thin wall A/C hose — standard R134a / R1234yf systems
• CA5 5-layer thin wall A/C hose — extra permeation resistance
• CA9 5-layer thick wall A/C hose — abrasion and heat duty
• EA48 refrigerated truck hose — −40 to +140°C, R404a / R410a tested
• Custom crimped A/C hose assemblies — built to drawing or OE number