Custom A/C Hose Assemblies Made to Your Drawing or Sample: How to Specify One That Quotes in 24 Hours
A custom air conditioning hose assembly is one of the easiest parts in the world to buy badly, and one of the easiest to buy well. The difference is almost never the manufacturing. It is whether the first email contained the three measurements that decide the part: inside diameter, end-to-end length and clock angle. Miss any one of them and you are not getting a quote - you are getting a question.
This guide is written for buyers who need assemblies made to a drawing, to a sample, or to nothing more than a photograph and a tape measure. It covers what to specify, how to measure a part you cannot draw, what the fitting names mean, and how a supplier should be qualifying the finished assembly before it ships.
What a "custom assembly" actually includes
Supplying hose by the metre and supplying a finished assembly are different jobs. A metre of barrier hose is a material. An assembly is that hose, cut to length, with fittings crimped on both ends, and then proven to hold refrigerant under pressure. The last step is the one most buyers forget to ask about, and it is the one that decides whether the part leaks at month three.
If you are buying hose by the metre, the specification conversation is simpler - see our guide to buying A/C hose by the metre. Everything below is about the finished, crimped part.
The specification checklist
| Item | Required? | Why it decides the quote |
|---|---|---|
| Hose inside diameter (ID) | Required | Sets the hose series and the ferrule size. Outside diameter alone is not enough - two hoses can share an OD and differ in wall thickness |
| Overall length | Required | State whether it is end-to-end (including fittings) or cut hose length. Getting this wrong is the single most common cause of a rejected first article |
| Fitting type, each end | Required | Straight, 45°, 90°, 135°, O-ring flange, quick connect or beadlock |
| Fitting size / thread | Required | -AN dash size, metric thread, or the OEM part number |
| Clock angle (orientation) | Required if either end is angled | The rotation between the two fitting ends, in degrees. Miss it and the assembly will not sit on the vehicle |
| Refrigerant | Required | R134a, R1234yf, R404a or R410a decides whether a barrier layer is mandatory |
| Working pressure / temperature | Recommended | Lets us confirm the hose class; 1.5 MPa and 3.5 MPa parts are not interchangeable |
| Quantity per size | Required | MOQ and tooling set-up are priced per size, not per order |
| End finish / marking | Optional | Caps, protective sleeves, part-number printing, barcode labels |
| Packing | Optional | Individual polybag, bundles of 10, carton quantity, pallet |
No drawing? Take these five measurements
Most workshops and distributors do not have a CAD file, and that is not a problem. In practice a photograph plus five numbers is enough to manufacture from. Here is what to measure, in order:
- Inside diameter of the hose - measure the bore, not the outside. If the hose is still on the vehicle, measure the outside diameter and count the wall thickness at a cut end; ID = OD minus twice the wall.
- Overall length, end to end - measure the finished assembly including the metal fittings, along the centreline. If the part is bent, follow the curve rather than measuring straight across; a hose that looks 700 mm across can be 850 mm along its route.
- Fitting size at each end - for -AN fittings, measure the thread outside diameter and count the threads per inch. For O-ring flange fittings, note the bolt-hole spacing. The OEM part number stamped on the fitting beats any measurement.
- Bend angle at each end - straight, 45°, 90° or 135°.
- Clock angle - this is the one people forget. Lay the assembly flat on a bench and photograph it from directly above. Then rotate one fitting until its opening points to "12 o'clock" and note how far the other fitting's opening has rotated away from that. That angle, in degrees, is the clock angle. A photo taken straight down with a clock or protractor in frame is worth more than a paragraph of description.
Fitting glossary
| Fitting style | What it looks like | Typical use |
|---|---|---|
| Straight | Fitting axis in line with the hose | Discharge and suction lines with generous routing space |
| 45° / 90° / 135° | Bent aluminium tube, crimped to the hose | Tight engine bays, compressor inlets, condenser connections |
| O-ring flange (block type) | Flat pad with bolt hole and O-ring groove | Compressor ports on most modern vehicles; sealed by the O-ring, not the thread |
| Quick connect | Plastic or metal female receiver that snaps onto a male tube | EV and late-model passenger cars; fast line assembly |
| Beadlock | Internal bead ring with a threaded collar; reusable | Field repair, off-road and motorsport where the joint is opened repeatedly |
| Custom machined | Made to your drawing or reverse-engineered from a sample | Machinery, refrigeration units, non-automotive equipment |
Fitting sizes are quoted in -AN dash or metric thread. Note that -AN dash sizes do not convert cleanly to the SAE J2064 nominal hose sizes used in passenger cars - if you are unsure, send the hose ID in millimetres and a photo of the fitting.
Barrier or non-barrier: the refrigerant decides
Refrigerant molecule size drives permeation, and permeation is why modern hose has an inner barrier layer. For R134a and R1234yf service, a barrier construction is the default; a non-barrier hose of the same size will lose charge measurably faster. Our explanation of the SAE J2064 types covers the permeability limits and why a permeation figure quoted without a test temperature tells you nothing. If your refrigerant is R404a or R410a for transport refrigeration, say so - those run at different temperatures and pressures and are specified differently.
How a qualified assembly is made
Our own sequence, start to finish:
- Specification review - we check ID, length, fitting combination, clock angle and refrigerant against a buildable configuration, and flag anything that looks like a suction-side part being specified for discharge duty.
- Hose selection - matched to refrigerant and pressure: CA5 five-layer thin wall, CA9 five-layer thick wall, EA4 four-layer, or EA48 for refrigerated transport. See the full range on our custom A/C hose assembly page.
- Sample or first article - for new drawings we recommend one sample before the production run.
- Cutting and crimping - cut square, insert to full depth, crimp with dies matched to that ferrule and hose combination. Verify the crimp diameter, not the machine pressure. The full procedure is in our crimping guide.
- Pressure testing - every assembly is pressure tested before packing.
- Packing and marking - part-number labels, individual sleeving and carton quantities to your specification.
What our test data actually shows
Numbers from our own hose qualification, so you can compare them with what your current supplier gives you:
| Test | Result | Context |
|---|---|---|
| Burst pressure | 35 MPa | Against a standard minimum of 13.7 MPa for this class of hose |
| Pressure hold | No leakage at 7.0 MPa | Held for the full test duration |
| Length change under pressure | 0% | No measurable growth - the reinforcement is doing its job |
| Wall thickness eccentricity | 0.15 - 0.33 mm | Against a 0.4 mm limit; low eccentricity is what keeps a crimp concentric |
Two of those four numbers matter more to you as a buyer than they look. Low eccentricity is what allows a clean, concentric crimp, and zero length change is what stops an assembly from pulling on its fittings once it is pressurised and hot.
Minimum quantities and lead times
- MOQ: 100 metres per size for hose supplied by the metre
- Assemblies are quoted per drawing; tooling set-up is priced per size
- Stocked sizes ship in 3-7 days
- New samples / first articles: typically 7-10 days after drawing approval, depending on fitting availability
- Size range in stock: 8.2 / 10.2 / 13.2 / 15.2 / 18.5 / 22.2 mm ID. If you are unsure which of those your part is, our size conversion chart and lookup tool will tell you in one step
Five mistakes that delay a custom hose order
| Mistake | What happens |
|---|---|
| Sending outside diameter as the size | Two hoses share an OD and differ in wall thickness - the ferrule will not match |
| No clock angle | The assembly is manufactured, then will not sit on the vehicle |
| Refrigerant not stated | You may be quoted a non-barrier hose for a barrier application |
| Length measured across the bend instead of along it | Assembly arrives short |
| Ordering a suction-side part for discharge duty | Larger-bore hose in our range is rated 1.5 MPa, not 3.5 MPa - it will fail on the high side |
Build your enquiry
Fill in the fields below and the tool writes a complete specification. Copy it into an email, or send it straight to WhatsApp. Sending the same text with a photo of the old part is usually enough for us to quote within 24 hours.
No upload, no sign-up. The text stays on your device until you choose to send it.
What happens after you send it
We reply within 24 hours with one of three answers: a quote, a request for the one measurement we still need, or - occasionally - an honest "this configuration will not hold pressure at that rating, here is what will". We would rather lose a day on that conversation than ship you a part that fails on a vehicle.
Related reading: buying A/C hose by the metre · SAE J2064 types explained · size chart and conversion · how to crimp assemblies.
Browse the hose range: CA5 five-layer thin wall · CA9 five-layer thick wall · EA4 four-layer · EA48 for refrigerated trucks.
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