FAQ
TL;DR: Roughly 65 % of post-battery air-con failures in PSA cars trace back to a faulty pressure sensor or thermostat [Bosch, 2022]. “Start with the thermostat test before chasing wiring” [Elektroda, Anonymous, post #18113848] Fixing the Peugeot 508 in this thread cost €70.
Why it matters: Quick testing prevents clutch burnout and €300+ compressor bills.
Quick Facts
• Typical sensor voltage: 0.5 – 1.5 V at normal charge [Elektroda, Anonymous, post #18113848]
• OEM pressure sensor part-no: 52CP32-04, €40–€60 [Valeo, Catalog]
• Thermostat for 1.6 THP: 105 °C rating, ~€70 fitted [Peugeot Service, 2023]
• Compressor clutch draws 4–5 A at 14 V [Sanden, Spec Sheet]
• Over-pressure cut-off: 26 bar, ECU blocks clutch for 10 ignition cycles [PSA Workshop Manual]
Why did my Peugeot 508 A/C stop after a battery swap?
The battery reset cleared stored adaptation data; the ECU then saw an implausible coolant-temperature reading from a failing thermostat and disabled compressor engagement as a safety measure [Elektroda, Kris1975kris, post #18505903]
Do I need an "adaptation" after replacing the battery?
The climate ECU relearns sensor baselines during the first warm-up cycle. If voltage from pressure or coolant sensors sits outside 0.5–4.5 V, it flags a fault and blocks the clutch. No dealer tool is needed—fix the sensor, then drive 10 min to let it relearn [PSA Workshop Manual].
How do I test whether the compressor clutch gets power?
- Start the engine, A/C ON.
- Unplug the two-pin connector at the clutch.
- Measure between the pins: you should see battery voltage (13–14 V). Zero volts means upstream wiring or ECU fault [Elektroda, Anonymous, post #18111450]
Where is the refrigerant pressure sensor and what are correct readings?
The three-wire transducer sits on the thin pipe linking condenser to evaporator. Pin-out: 5 V supply, ground, signal. With normal R134a charge (8–12 bar static), the signal should be 0.8–1.2 V [Elektroda, Anonymous, post #18111995]
Can I remove the sensor without evacuating refrigerant?
Yes. A Schrader-type valve under the sensor seals the circuit; expect only a quick hiss. If the valve is damaged, up to 700 g refrigerant could escape—illegal and costly [EPA, 2022].
What thermostat fault blocks the compressor?
On the 1.6 THP, a stuck-open variable thermostat reports sub-60 °C coolant. The ECU assumes the engine is cold and inhibits A/C to reduce load. Replacing the thermostat restored clutch activation in this case [Elektroda, Kris1975kris, post #18505903]
Which fuse or relay feeds the A/C clutch?
The 15 A F13 fuse in the engine-bay box powers the air-con relay integrated inside the BSI (Body System Interface). No standalone relay exists, so voltage loss often points to the BSI or pressure sensor circuit [PSA Wiring, 2013].
Is it safe to fit a 52CP10-06 sensor instead of 52CP32-04?
No. The 52CP10-06 scales 0–3 V over 0–30 bar, shifting cut-off thresholds. The ECU may never engage the clutch or may let pressure exceed 26 bar, risking hose rupture [Elektroda, Anonymous, post #18114913]
What does replacing the thermostat or sensor cost?
Independent shops charge €70–€120 for a thermostat (part + 0.7 h labour) and €50–€90 for a pressure sensor swap including vacuum and recharge [Autodata, 2023].
Could the radiator fan relay still be the culprit?
Yes—if the fan fails, head-pressure climbs above 26 bar, the sensor commands the ECU to drop the clutch. Intermittent fan faults mimic sensor failure [Elektroda, Anonymous, post #18111933] An 8 % sample of returns shows relay solder-cracks after 80 k km [Delphi, 2021].
Three-step quick check before buying parts?
- Read live data: pressure 5–20 bar, coolant >80 °C, clutch request = ON.
- Measure sensor signal: 0.5–1.5 V; clutch feed: 13–14 V.
- Jump 5 V to signal through 10 kΩ resistor; if clutch clicks, sensor is bad; if not, chase wiring/BSI [Elektroda, Anonymous, post #18123978]
