How to Test the AC Relay in a PT Cruiser
The A/C relay in your PT Cruiser allows a high-current compressor clutch circuit to be controlled by a low-current switch. Turning the A/C controls to the "on" position sends a signal to the on-board computer to supply ground to the control side of the relay and turn on the compressor clutch. Testing requires the use of an automotive circuit tester. This prevents damage to the computer that can occur if a common test light is used.
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Instructions
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1
With the engine running, turn the A/C controls to the max A/C position, and remove the A/C relay from the power distribution block. Attach the red lead of the circuit tester to the positive battery terminal, and the black lead to the negative battery terminal. Locate the two terminals in the power distribution block that supply power to the relay. If power is not found at the distribution block, check for blown fuses or fusible links.
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2
Locate the ground terminals for the circuit in the power distribution block, and test for ground. If no ground is found on the high-current side, check the compressor clutch. If no ground is found on the control side, check the computer and pressure switches in the system.
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3
Plug the relay back in and check for power at the compressor clutch. If power and ground testing checks out, but power is not supplied to the compressor when the relay is plugged in, replace the relay. If power is present at the clutch, but the clutch does not function, replace the compressor.
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Tips & Warnings
Further information regarding Step 1 can be found in your service manual or in an online resource like AllDataDIY. See "Resources," below, for more information on the AllDataDIY system.
