Tools & consumables
- Refrigerant recovery/recharge machine (certified) or fully charged refrigerant cans + recovery bottle if local law permits (do NOT vent to atmosphere).
- Manifold gauge set for the system refrigerant (R‑134a or specified) with low/high hoses and quick‑couplers.
- Vacuum pump (rotary vane) and a digital micron gauge.
- Refrigerant scale (0.1 oz/1 g resolution).
- Leak detector (electronic refrigerant sniffer) and UV dye + UV lamp (optional).
- Infrared thermometer or thermocouples for evaporator outlet and condenser outlet temps.
- Basic hand tools: wrenches, pliers, screwdrivers, socket set.
- O‑rings (assorted sizes compatible with refrigerant oil), PAG oil (type & amount per compressor spec), replacement receiver/drier or accumulator, replacement orifice tube/expansion valve if fitted and suspected bad.
- Safety PPE: safety glasses, nitrile gloves, long sleeves, face shield if available. Nitrogen bottle with regulator for pressure testing (optional).
- Battery charger or stable 12 V supply to run fan/compressor clutch during test.

Safety & legal
- You must recover refrigerant — do not vent. In many regions certification (eg. EPA 608) is required to handle refrigerant. Follow local laws.
- Refrigerant and oil cause severe frostbite on contact. Wear gloves and eye protection.
- Work in a well‑ventilated area. Avoid inhaling refrigerant.
- Disconnect battery when removing electrical components; reconnect for compressor clutch checks only.
- Use nitrogen for leak/pressure tests only with a regulator and relief protection; do not exceed system design pressure.

Quick system notes (Perkins 4.107/4.108/4.99 installations)
- The A/C system is vehicle/application dependent. Identify refrigerant type and system charge from vehicle data plate or workshop manual before starting.
- Compressor is engine‑driven — check belt condition and tension, and compressor clutch operation before charging.

Step‑by‑step procedure

1) Preparation & identification
- Confirm refrigerant type (R‑134a or other) and exact charge amount from vehicle/data plate or workshop manual. If not available, log out system and charge by weight to factory spec — do NOT guess.
- Visually inspect system for oil stains, damaged hoses, corroded fittings, collapsed hoses, bent condenser fins or damaged compressor clutch.
- Check electrical fuse and wiring to compressor clutch. Slowly spin compressor clutch by hand with belt removed to check for roughness.

2) Leak detection & repair (do not charge until leaks fixed)
- Connect electronic leak detector and scan entire line set, fittings, condenser, evaporator core area, compressor shaft seal and service ports.
- If a leak is found, repair or replace the failed component (hose, fitting, condenser, evaporator, O‑ring). Replace O‑rings with refrigerant‑compatible and pre‑lubricate with correct PAG oil.
- If no obvious external leak, pressurize with dry nitrogen to ~150–200 psi (or manufacturer test pressure) and use soapy water or detector to find leaks. Do not exceed safe pressure. Evaporator leaks may require removal and bench pressure testing.

Parts commonly replaced when opening system
- Receiver/drier or accumulator: replace any time the system is opened to atmosphere or when moisture contamination suspected.
- O‑rings at service ports and quick couplers.
- Compressor shaft seal (if leaking) or full compressor if clutch/compression failure.
- Orifice tube or TXV/expansion valve if clogged or contaminated.

3) Recover existing refrigerant
- If refrigerant is present, use a recovery machine to evacuate the existing charge into an approved recovery cylinder. Note recovered weight if you will reuse recycled gas per regulations.

4) Replace receiver/drier & clean connections
- Drain/disconnect and replace accumulator/receiver‑drier/filters. Replace any O‑rings and add correct amount/type of PAG oil to the compressor if specified or if compressor was removed.
- Tighten fittings to proper torque.

5) Evacuate
- Connect manifold gauges to low (suction) and high (discharge) service ports. Hook vacuum pump to center hose via manifold.
- Run vacuum pump and pull down to 500 microns (0.5 torr) ideally. At minimum hold 25–29 inHg for 30+ minutes but use a micron gauge for accuracy.
- Hold vacuum for 10–20 minutes after pump off to confirm no rise (leaks) and that system is dry. If vacuum rises, find and fix leak; repeat evacuation.

Tool use tips:
- Manifold gauges: low port = blue (suction), high port = red (discharge). Open both valves to evacuate; close high when charging by low. Always keep gauges connected to read pressures.
- Vacuum pump: connect through manifold center; run continuously until target micron achieved. Use micron gauge between pump and system — do not rely on pump vacuum gauge alone.

6) Charging — by weight (preferred)
- Connect refrigerant cylinder to recharge hose on the recovery/recharge machine or manifold with a scale under cylinder.
- Start engine and engage A/C (blower high, temp cold, compressor clutch engaged). Turn on condenser fan(s) as needed.
- With manifold low side open and high side open as manufacturer recommends for charge procedure, add refrigerant slowly while watching scale. Add liquid only where specified (many systems require charging in vapor — usually charging into low side in vapor state). Follow factory instructions.
- Charge to the exact factory mass (grams/oz). If you don’t have a spec, do NOT “top off” by sight; instead use superheat/subcooling method (see below).

7) Charging — by performance (if mass unknown)
- Allow system to stabilize (compressor running for several minutes).
- Measure low side pressure and corresponding evaporating saturation temperature from R‑134a pressure/temperature chart. Measure actual evaporator outlet air temp (thermocouple) and calculate superheat: Superheat = Saturation temp (from low side pressure) − Evaporator outlet air temp (sensor in evaporator discharge).
- Target typical evaporator superheat: 8–12 °F (4–7 °C) for fixed orifice systems; target may differ with TXV systems where low superheat 2–5 °F is normal. Use factory spec when available.
- Measure condenser outlet liquid line temperature and calculate subcooling: Subcooling = Saturation temp (from high side pressure) − Liquid line temperature. Typical subcooling target 8–14 °F. Adjust refrigerant amount slowly to hit desired superheat/subcooling.
- Always add small amounts, then wait to stabilize (a few minutes) before re‑measuring.

Tool use tips:
- Refrigerant scale: zero with cylinder on scale and record weight consumed during charging. This is the most accurate method.
- Thermometers: place one sensor on liquid line (just after condenser) and one in evaporator discharge duct.

8) Validate system operation
- Confirm compressor cycles normally, clutch engages, and fans run when commanded.
- Check pressures with gauges at operating ambient (document readings). Low and high pressures should be reasonable for ambient temperature (consult chart or manual).
- Check discharge air temp at vents — should be significantly colder (20–40 °F below ambient depending on system and ambient temperature).
- Run system 10–15 minutes and re‑check superheat/subcooling; fine tune charge if necessary.

9) Final checks & cleanup
- Cap service ports, remove manifold hoses, and torque caps appropriately.
- Scan for leaks again with electronic detector after charging.
- Properly label service done and refrigerant amount added.
- Dispose of used parts and recovered refrigerant per regulations.

Common pitfalls & how to avoid them
- Adding refrigerant without repairing leaks: fixes nothing; you’ll lose charge quickly.
- Not evacuating moisture: moisture causes acid and blockages — always pull a good vacuum.
- Overcharging: causes high head pressures, poor cooling, compressor damage. Use weight or superheat/subcooling method.
- Using wrong refrigerant or wrong oil type: mismatch clogs or destroys compressor.
- Venting refrigerant to atmosphere: illegal in many jurisdictions; always recover.
- Not replacing receiver/drier after opening the system: moisture will remain and damage system.
- Charging too quickly: can flood compressor with liquid; add slowly with system running.
- Relying only on gauge pressures and not checking temperatures/superheat/subcooling.

Replacement parts usually required when opening system
- Receiver/drier or accumulator
- Service port caps and O‑rings
- PAG oil (compressor oil top‑up/specified amount)
- Orifice tube/expansion valve (if clogged)
- Condenser/evaporator or hoses if leaking or corroded
- Compressor or clutch if seized or leaking

Closing notes (short)
- Always follow vehicle/workshop manual charge spec. Charge by weight is best. Use proper recovery equipment and PPE. Replace receiver/drier when system is opened. Pull to deep vacuum (microns), test for leaks, then charge slowly and verify by superheat/subcooling.
rteeqp73

Diesel Exhaust Fluid | Perkins Engines If you're using a selective catalytic reduction (SCR) system you need diesel exhaust fluid (DEF) for the system to work.

Compression Testing a Diesel Engine | Perkins 4 Cylinder Diesel I do a compression test on my Perkins 4 Cylinder Diesel engine in my JCB 208s (1CX) to make sure it's good on the inside.

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