Powertrain, generic

P0EC7 A/C Power Supply Relay Control Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P0EC7 is set when the control line of the relay feeding the A/C reads too low a voltage, usually because it is shorted to ground. What the driver feels depends on how the coil is switched: with a low-side driver a grounded line can keep the relay energised even with the A/C off, while with a high-side driver the relay simply cannot be switched on. No manufacturer documents P0EC7 publicly. As a comparison, Mitsubishi monitors a relay-fed supply on its throttle actuator (P0657): with battery voltage above 8.3 V, the switched line must not sit at or below 6.0 V for 0.35 seconds. Open-circuit code: P0EC6; high counterpart: P0EC8; clutch relay analogue: P0646.

Likely causes

Relay control line chafed and shorted to ground
Shorted turns in the relay coil
Output stage of the module stuck low

Symptoms

  • A/C power stays on with A/C switched off, or never switches on
  • Possible battery drain while parked if the relay stays energised

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€20–350
Time0.5–2 h

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

Parts involved

ac power supply relayhvac control modulewiring harness

Related codes

P0EC6P0EC8P0646

References: mitsubishitechinfo.com, law.cornell.edu.