Code
P1620
DAEWOO
P — Powertrain
A/c relay
Views:
UK: 5
EN: 7
RU: 10
AI status
Completed
Completed
100%
Causes
- Failed A/C relay (stuck open or shorted)
- Blown fuse protecting A/C relay or compressor circuit
- Open, shorted, or corroded wiring/connectors in relay control or power feed
- Poor ground at relay or compressor clutch
- Faulty A/C compressor clutch or coil
- Faulty control module (ECM/BCM) driver output
Symptoms
- Air conditioning does not engage (no compressor clutch operation)
- No cooling from HVAC when A/C selected
- Relay may click intermittently or not at all
- Possible blown fuse or tripped circuit protection
- Malfunction Indicator Lamp (MIL) or service message in some vehicles
What to check
- Verify stored freeze-frame/fault data with a scan tool; confirm P1620 and any related codes
- Visually inspect A/C relay, fuse, relay socket and wiring for damage or corrosion
- Swap the suspect relay with a known-good same-type relay (from another circuit) to see if behavior changes
- Check continuity and resistance of relay coil and compressor clutch coil (with ignition OFF)
- Measure voltage at relay power terminal and at the relay control terminal when A/C is requested
- Check ground integrity at relay and compressor clutch
Signal parameters
- Battery supply to relay power terminal: approximately battery voltage (~12–14.5 V) with ignition ON
- Relay control/coil activation signal: changes state when A/C request is made (either pulled to ground or supplied with 12 V depending on vehicle design)
- Relay coil resistance (typical): commonly ~50–200 ohms (manufacturer-specific — compare to known-good)
- Compressor clutch feed: 12 V present at clutch terminal when relay is energized (verify with A/C request)
- Control module output: toggles between ~0 V and battery voltage when commanding relay (confirm with scope or DVOM)
Diagnostic algorithm
- Retrieve all related DTCs and freeze frame data. Note whether the code is current, pending, or historical.
- Inspect fuses and relays in the A/C circuit; replace any blown fuse and test with a known-good relay if available.
- With ignition OFF, unplug the A/C relay and inspect socket and connector for corrosion, burned terminals, or looseness. Repair as needed.
- Measure relay coil resistance on the bench (if removed) and compare to specification or to a known-good relay.
- With back-probes on the relay socket and ignition ON, command A/C ON via switch or scan tool and measure: battery feed voltage, control signal voltage, and ground continuity. Expect battery voltage on feed and a change on control terminal when requested.
- If relay control signal is present but compressor clutch does not engage, measure at the compressor clutch connector for voltage when commanded; check clutch coil resistance and ground.
- If control module output never changes when A/C is requested but wiring is intact, inspect wiring harness continuity back to the ECU/BCM and consider ECU driver fault.
- If wiring and relay are good but intermittent behavior remains, consider wiring harness repair, connector replacement, or replacement of relay and retest.
- Clear codes and road-test or operate A/C to verify repair; monitor for reappearance of P1620.
Likely causes
- A/C relay contacts failed or coil open/short
- Connector corrosion or loose terminal at relay socket
- Damaged fuse or incorrect fuse rating
- Open/shorted wire between relay and compressor clutch
- Control module unable to drive relay due to internal fault
Fault status
Status
P1620 — A/C relay circuit fault detected. Control module has identified an abnormal condition in the air conditioning relay/control circuit that may prevent compressor engagement.
Repair difficulty: Medium
Diagnostic time: 0.5 - 1.5 hours
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