Toggle Side Panel

Shopping Cart

No products in the basket.

Shopping Cart

No products in the basket.

Close search
Home / DTC / B1079 — A/C refrigerant leak

B1079 — A/C refrigerant leak

Detailed page for trouble code B1079.

34,405codes
59brands
11,914generic
22,491specific
All codes P-codes (Powertrain) B-codes (Body) C-codes (Chassis) U-codes (Network/User) Tesla Alerts
Reset
Code

B1079

MITSUBISHI B — Body

A/C refrigerant leak

Brand: MITSUBISHI
Type: B — Body
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Actual refrigerant leak in A/C system (hose, joint, condenser, evaporator, compressor shaft seal, O‑rings)
  • Failed or out-of-spec refrigerant pressure/level sensor or leak-detection sensor
  • Corroded or damaged service ports, fittings or O‑rings
  • Faulty wiring, poor connector contact, or blown fuse/relay for A/C sensors or control circuit
  • Insufficient system charge from previous service or improper recharge

Symptoms

  • Weak or no A/C cooling (reduced cabin cooling)
  • Compressor clutch cycles rapidly or does not engage
  • Refrigerant smell or oily residue around A/C components
  • A/C warning or service message on dash (model dependent)
  • Stored DTC B1079 and possibly related codes

What to check

  • Scan for stored/active codes and freeze frame data; note accompanying codes
  • Visual inspection for oily residue, UV dye, corrosion or physical damage at hoses, fittings, condenser, evaporator housing and compressor shaft
  • Measure static system pressure (engine off) and low/high side pressures with manifold gauges (engine off and running, A/C on)
  • Check compressor clutch operation and A/C relay/fuse status
  • Inspect pressure sensor/leak-detection sensor wiring and connectors for corrosion, damage or poor contact
  • Use an electronic leak detector or UV dye/black light to locate leaks

Signal parameters

  • Static system pressure (cold ambient) — expected to be near ambient vapor pressure; very low indicates lost charge
  • High/low side pressures with A/C on — compare to typical values for ambient temperature (use vehicle-specific chart)
  • Refrigerant pressure sensor voltage (typical 0.5–4.5 V range depending on model) or digital sensor reading
  • Compressor clutch control signal (ON/OFF) from A/C control module
  • Leak detector output (if equipped) or presence/absence of UV dye at suspected leak points
  • Ambient temperature and evaporator inlet/outlet temperatures for performance comparison

Diagnostic algorithm

  1. Retrieve DTCs and freeze frame with a scan tool; record operating conditions when code set (ambient temp, engine speed, A/C switch state).
  2. Perform a careful visual inspection of A/C components (hoses, connections, condenser, evaporator area inside dash if accessible) for oil/dye stains or damage.
  3. Check fuses, relays and wiring to A/C pressure/leak sensors and control module; repair any damaged wiring or poor connections.
  4. Using manifold gauges, measure static pressure (engine off) and then pressures with engine running and A/C on; note if pressures are abnormally low.
  5. If low charge suspected, use an electronic refrigerant leak detector and/or UV dye introduced to the system (if safe and previously used) to pinpoint leak location.
  6. If leak not found visually, perform a low-pressure nitrogen decay test at service ports (limit pressure to safe value per manufacturer) and observe for pressure drop; apply soap solution to fittings and components to locate bubbles.
  7. Inspect and test the refrigerant pressure sensor and leak-detection sensor: measure sensor voltage/outputs and compare to specifications; check continuity and grounds on wiring harness.
  8. Repair or replace the leaking component(s) or failing sensor(s). Replace O‑rings, drier/accumulator and Schrader valves as needed when opening the system.
  9. Evacuate the system with a vacuum pump and hold vacuum to confirm no remaining leaks (commonly 30+ minutes or as specified).
  10. Recharge the system to the manufacturer-specified refrigerant type and charge weight. Recharge oil quantity as required.
  11. Re-test system operation (pressures, temperatures, compressor engagement) and perform a road or operational test. Re-scan for codes and clear DTCs; monitor for recurrence.

Likely causes

  • Oil or dye residue visible at a hose connection, condenser or evaporator indicating a leak
  • Low static or running refrigerant pressure on manifold gauges
  • Pressure sensor output voltage out of expected range or erratic readings
  • Compressor clutch not engaging because system low‑pressure cutout is active
  • Dry or collapsed accumulator/drier or failed Schrader/service valve

Fault status

⚠️ Status
A/C refrigerant leak detected or low refrigerant level — system may be undercharged or leak sensor/sensor circuit fault. DTC B1079 stored.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

B1078 B1080 B1081 P0440 P0442 P0530
406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

MITSUBISHI

Your experience will help others
+100 karma for a short comment :)
Keep it short and practical. Up to 500 characters.
Send to email

Report

Harassment or bullying behavior
Contains mature or sensitive content
Contains misleading or false information
Contains abusive or derogatory content
Contains spam, fake content or potential malware

Block Member?

Please confirm you want to block this member.

You will no longer be able to:

  • See blocked member's posts
  • Mention this member in posts
  • Invite this member to groups
  • Message this member
  • Add this member as a connection

Please note: This action will also remove this member from your connections and send a report to the site admin. Please allow a few minutes for this process to complete.

Report

You have already reported this .