AutoCodes – Ford – P0645 1997 Ford F150

P0645 1997 Ford F150 Code - Wide Open Throttle A/C Cutout Primary Circuit Malfunction

Quick Answer

A/C clutch relay may also be referred to as A/C compressor clutch relay. Common causes include Faulty Air Conditioning Clutch Relay, Air Conditioning Clutch Relay harness is open or shorted, Air Conditioning Clutch Relay circuit poor electrical connection. 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: P0645 1997 Ford F150 indicates Wide Open Throttle A/C Cutout Primary Circuit Malfunction .
Common causes: Common causes include Faulty Air Conditioning Clutch Relay, Air Conditioning Clutch Relay harness is open or shorted, Air Conditioning Clutch Relay circuit poor electrical connection.
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.

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Code Popularity 2,349

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 01, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0645 1997 Ford F150 Description

A/C clutch relay may also be referred to as A/C compressor clutch relay. A/C clutch relay circuit is monitored when ignition is on and battery voltage is greater than 10.4 volts.

OBDII Code P0645 1997 Ford F150 - Wide Open Throttle A/C Cutout Primary Circuit Malfunction - AutoCodes.com — P0645 1997 Ford F150 Code - Wide Open Throttle A/C Cutout Primary Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P0645 1997 Ford F150?

Faulty Air Conditioning Clutch Relay
Air Conditioning Clutch Relay harness is open or shorted
Air Conditioning Clutch Relay circuit poor electrical connection
Damaged PCM

How to Fix the DTC P0645 1997 Ford F150?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

For applications that use a normally open relay to control the A/C clutch, the following description applies to the A/C clutch relay control circuit.
Monitors the wide open throttle A/C cutoff (WAC) circuit output from the PCM. The test fails if: When the PCM grounds the WAC circuit, excessive current draw is detected on the WAC circuit; or with the WAC circuit not grounded by the PCM, voltage is not detected on the WAC circuit (the PCM expects to detect VPWR voltage coming through the WAC relay coil to the WAC circuit).

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0645 1997 Ford F150 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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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.

Frequently Asked Questions about P0645 1997 Ford F150 Code

1. What does the OBDII code P0645 mean for a 1997 Ford F150?

Code P0645 indicates a malfunction in the Wide Open Throttle (WOT) A/C cutout primary circuit, which helps disable the A/C compressor under heavy acceleration.

2. What are the common symptoms of a P0645 code in a 1997 Ford F150?

Symptoms include the A/C system not functioning properly, the check engine light illuminating, and reduced engine performance during acceleration.

3. What causes the P0645 code to trigger on a 1997 Ford F150?

Possible causes include a faulty A/C relay, wiring issues such as shorts or open circuits, a malfunctioning PCM, or a defective WOT A/C cutout switch.

4. Can a P0645 code affect engine performance?

Yes, it can. If the A/C system does not disengage during wide open throttle, it may reduce engine power and efficiency during heavy acceleration.

5. How do I diagnose the P0645 code on a 1997 Ford F150?

Start by visually inspecting the A/C relay, wiring, and connectors for damage or corrosion. Then use a multimeter to test the relay and check the circuit for proper voltage and continuity.

6. Can I drive my 1997 Ford F150 with a P0645 code?

While itâ€™s possible to drive with this code, itâ€™s recommended to address it promptly as it may impact A/C system operation and engine performance.

7. How is the P0645 code fixed on a 1997 Ford F150?

Repairs may include replacing the A/C relay, repairing or replacing damaged wiring, or reprogramming or replacing the PCM if itâ€™s determined to be the cause.

8. How much does it cost to fix a P0645 code on a 1997 Ford F150?

Repair costs vary but typically include the cost of diagnosing the issue (around $75-$150) and parts like a new relay or wiring repair, which can range from $10 to $200, depending on the issue.

9. Can a bad PCM cause the P0645 code on a 1997 Ford F150?

Yes, a malfunctioning PCM can cause the P0645 code if it fails to properly control the WOT A/C cutout circuit.

10. How can I prevent the P0645 code from occurring on my 1997 Ford F150?

Regularly inspect and maintain your vehicleâ€™s electrical components, including the A/C relay and wiring, and address any issues promptly to avoid circuit malfunctions.