A/C Signal: Description and Operation

1993 Plymouth Laser FWD L4-1753cc 1.8L SOHCSECTION Description and Operation

A/C Circuit:






Operation
When the driver turns on the A/C system, a positive voltage signal is supplied to the ECM (as an indication that the A/C system is needed) and to one side of the A/C relay coil, located on the left fender apron near the firewall.

The ECM determines if engine conditions are suitable for A/C operation (idle speed, ignition timing and air/fuel mixture). If the ECM senses that conditions are suitable for A/C operation, it supplies the ground circuit for the A/C relay coil, energizing it. This allows the relay to supply voltage to the compressor clutch.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.