Faulty evaporator temperature sensor (open or short internally, or reading drift); Damaged, chafed or corroded wiring to the sensor (open circuit, short to earth or short to supply); Poor connection at the sensor or control unit connector (corrosion, loose or pushed-out pin, water ingress); Sensor poorly seated or incorrectly fitted in the evaporator housing, giving false readings; Fault in the A/C or climate control module or the engine control unit processing the signal; Low refrigerant charge or restricted system causing readings that do not match expectations.

P0535

A/C Evaporator Temperature Sensor Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
5: AreaVehicle speed, idle control and auxiliary inputs
35: FaultThe specific fault in that area

What it means

P0535 is the generic SAE J2012 code for a fault in the A/C evaporator temperature sensor circuit. The control unit monitors the sensor's signal voltage and sets the code when it is outside the expected range or does not make sense for the conditions. The evaporator temperature sensor is used to help prevent the evaporator freezing up and to manage compressor operation.

Symptoms

A/C blows warm or not as cold as normal
A/C compressor does not engage or cycles erratically
Evaporator freezing up, giving reduced airflow from the vents
Air conditioning warning or fault message on some models
Slightly raised idle or engine load changes when the compressor cycles oddly

Possible causes

Faulty evaporator temperature sensor (open or short internally, or reading drift)likely
Damaged, chafed or corroded wiring to the sensor (open circuit, short to earth or short to supply)likely
Poor connection at the sensor or control unit connector (corrosion, loose or pushed-out pin, water ingress)likely
Sensor poorly seated or incorrectly fitted in the evaporator housing, giving false readingspossible
Fault in the A/C or climate control module or the engine control unit processing the signalrare
Low refrigerant charge or restricted system causing readings that do not match expectationspossible

How to diagnose

Read all stored codes and freeze frame data, and note whether the code is current or intermittent
Check live data for evaporator temperature and compare it with cabin air temperature on a cold-soaked car; a reading stuck at an extreme suggests an open or short
Inspect the sensor wiring and connector for chafing, corrosion, water and bent or pushed-out pins
Wiggle the harness with the engine running and the A/C on while watching the live reading for dropouts
Check the sensor is correctly located in the evaporator housing; its position and access vary by model
Measure sensor resistance and compare it with the manufacturer's specification at a known temperature
Check the reference voltage, signal and earth at the sensor connector, and test the wiring for continuity and shorts
Check A/C refrigerant pressures and the system's performance to rule out a genuine cooling fault

How to fix

Replace the evaporator temperature sensor if it is out of specification or faulty
Repair or replace damaged wiring and terminals in the sensor circuit
Clean, secure or replace the affected connector and reseat the pins
Refit the sensor correctly in its mounting position
Repair any refrigerant leak and recharge the system to specification if the A/C fault is genuine
Replace or repair the control unit only after the sensor and wiring have been proven good

Can I keep driving?

Low severity

The car is normally safe to drive as this affects comfort and A/C operation rather than engine safety. Book it in soon, as a frozen evaporator or stressed compressor can lead to further A/C faults.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.