Body, generic

B0292 HVAC A/C Compressor Clutch Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Whether B0292 is used anywhere is unknown; no consulted J2012 list carries it and no maker documents it. Its title points to the electromagnetic clutch that couples a belt-driven compressor to its pulley, and the relay feeding the clutch coil. Usually the engine controller owns this circuit and logs P0645–P0647; on the Saab 9-3 with Trionic 8, for instance, P0646 sets when the relay output stays below 2 V for over 1 s, and the compressor may then run without stop. Patent US20040211197A1 explains that the climate unit cannot see a failed clutch unless an extra feedback path exists, and US4481784A shows the classic battery–relay–coil chain. Electric compressors without a clutch do not use such a code.

Likely causes

Clutch coil open or shorted, often after overheating
A/C clutch relay failed or contacts welded
Excessive clutch air gap so the plate does not pull in
Clutch feed or ground wire at the compressor damaged by heat

Symptoms

  • No cooling, compressor hub does not turn with A/C on
  • Compressor runs permanently even with A/C switched off

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–600
Time0.3–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ac compressor clutchac compressor relayhvac control module

Related codes

P0645P0646P0647B0288

References: saabwisonline.com, saabwisonline.com, patents.google.com, patents.google.com.