P053515

Code

VOLVO P — Powertrain

A/C Evaporator Temperature Sensor Circuit. Circuit Short To Battery or Open

Brand: VOLVO

Type: P — Powertrain

Views: UK: 17 EN: 34 RU: 16

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Page language: EN

Causes

Damaged or chafed wiring harness to evaporator temperature sensor
Corroded, pushed-out, or water-intruded connector at the sensor
Failed evaporator temperature sensor (thermistor)
Short to battery (wire pinched to 12V feed) or open circuit in the sensor circuit
Blown fuse, failed A/C relay, or connector supplying sensor reference voltage
Control module (HVAC/BCM/ECM) internal fault or poor ground

Symptoms

A/C system may be disabled or run in limp mode
Compressor may not engage or cycles incorrectly
HVAC displays wrong evaporator temperature or error/warning in climate menu
Interior may not reach requested set temperature
Evaporator may freeze up because of incorrect temperature feedback

What to check

Read freeze frame and live data from HVAC/BCM/ECM to confirm evaporator sensor status and any related codes
Visually inspect sensor connector and wiring for corrosion, damage, pinch points, or water intrusion
Check relevant fuse(s) and A/C relays
Backprobe connector and measure reference voltage and signal while key ON and with A/C on
Measure sensor resistance at connector with sensor disconnected (compare to expected thermistor behavior)
Check continuity to control module pin and for shorts to battery/ground with wiring disconnected

Signal parameters

Sensor type: typically a thermistor (negative temperature coefficient) — resistance decreases as temperature rises
Typical signal wiring: reference/ground and signal to HVAC/BCM (module usually uses ~5V reference or ground reference)
Expected behavior: signal voltage varies with evaporator temp; typical usable range ~0.5–4.5 V at the module under normal temps (varies by model)
Open-circuit condition: signal may read extreme/high or float; short-to-battery: presence of vehicle battery voltage on the sensor circuit or abnormally high voltage at module pin

Diagnostic algorithm

Retrieve all HVAC/BCM/ECM codes and live data. Note freeze frame and whether the code is current or historic.
Visual inspection: access evaporator temperature sensor (usually in HVAC housing/evaporator core area). Inspect connector for corrosion, moisture, or damage; inspect harness routing across firewall and heater box for chafes or pinches.
With ignition ON (A/C enabled), backprobe the sensor connector: identify reference (5V), signal, and ground pins from wiring diagram. Verify reference voltage present and good ground. If reference missing, trace to fuse/relay/module.
Measure signal voltage with sensor connected while changing cabin temp (or using canned air on evaporator) to see voltage change. No change suggests open/short or failed sensor.
With ignition OFF, disconnect sensor and measure sensor resistance between its signal and ground terminals. Check resistance vs. temperature: thermistor should change smoothly (not open or infinite). If open or infinite, replace sensor.
Check for short to battery: with ignition OFF, measure for battery voltage on the signal wire at the connector. If ~12V present, isolate harness and locate where it contacts a 12V feed (inspect near connectors, harness splices, relays).
Check continuity from sensor connector to HVAC/BCM pin to rule out internal harness break. Check resistance to chassis ground where applicable.
If wiring and sensor pass tests but fault persists, inspect/replace HVAC control module or repair its connector after verifying module pins not damaged and module software is current.
After any repair, clear codes and perform a functional test (start vehicle, enable A/C, monitor evaporator temp signal and A/C operation).

Likely causes

Corroded/wet connector at evaporator sensor (common in HVAC evaporator area)
Broken/frayed harness where it passes the firewall or near evaporator housing
Failed thermistor-style evaporator temperature sensor
Wire pinched and contacting a 12V feed (short-to-battery)

Fault status

⚠️ Status

A/C evaporator temperature sensor circuit has detected an open or a short-to-battery condition; evaporator temperature signal invalid or out of range.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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