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P0646 Chrysler Code - Low Voltage Detected At The AC Clutch Relay

Quick Answer

When the diagnostic trouble code P0646 appears in a Chrysler vehicle, it indicates that the Powertrain Control Module (PCM) has detected low voltage at the AC clutch relay. Common causes include Faulty AC clutch relay, Wiring issues such as a short circuit or open circuit, Defective PCM. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means
P0646 Chrysler indicates Low Voltage Detected At The AC Clutch Relay.
Common causes
Common causes include Faulty AC clutch relay, Wiring issues such as a short circuit or open circuit, Defective PCM.
Severity
Low - monitor the vehicle and repair when practical.
Can I drive?
The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.
What is this?
Table of contents Created and updated by William Orellana on Aug 30, 2024
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Code P0646 Chrysler Description

When the diagnostic trouble code P0646 appears in a Chrysler vehicle, it indicates that the Powertrain Control Module (PCM) has detected low voltage at the AC clutch relay. The AC clutch relay is responsible for engaging and disengaging the air conditioning compressor, which plays a crucial role in the vehicle's climate control system. Low voltage at the relay can prevent the compressor from functioning properly, leading to a lack of cold air inside the cabin. This issue can impact the comfort of the vehicle's occupants, especially during hot weather conditions.

OBDII Code P0646 Chrysler - Low Voltage Detected At The AC Clutch Relay
P0646 Chrysler Code - Low Voltage Detected At The AC Clutch Relay

Common Causes of P0646 Chrysler

  1. Faulty AC clutch relay.
  2. Wiring issues such as a short circuit or open circuit.
  3. Defective PCM.
  4. Low refrigerant levels in the AC system.
  5. Electrical system malfunctions.

Symptoms of P0646 Chrysler

  1. Lack of cold air coming from the air conditioning system.
  2. Inconsistent cooling performance, with the air conditioning working intermittently.
  3. Unusual noises coming from the compressor when the AC is engaged.
  4. The AC compressor clutch failing to engage or disengage properly.
  5. Illumination of the check engine light on the dashboard.

How to Fix P0646 Chrysler

  1. Begin by verifying the presence of the P0646 code using an OBD-II scanner and diagnosing the specific cause of the low voltage at the AC clutch relay.
  2. Inspect the wiring connected to the AC clutch relay for any signs of damage or corrosion. Repair or replace any damaged wiring as needed.
  3. Test the AC clutch relay to determine if it is functioning correctly. Replace the relay if it is found to be defective.
  4. Check the refrigerant levels in the AC system to ensure they are within the manufacturer's specifications. Recharge the system if necessary.
  5. Clear the trouble code from the PCM's memory and test the AC system to confirm that the issue has been resolved.

Cost to Fix P0646 Chrysler

The cost of repairing the low voltage detected at the AC clutch relay in a Chrysler vehicle can vary depending on the specific cause of the issue and the cost of replacement parts. In general, the repair may range from $100 to $300, including parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's recommended to obtain a detailed quote from a trusted mechanic before proceeding with the repair.

When is the Code Detected?

Code P0646 may be stored if the commanded signal from the AC Clutch circuit does not match the feedback signal.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

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