🚨 Diagnostic Profile
Vehicle Make: Chrysler
Fault Description: A/C Request Circuit High Voltage
This condition indicates that the HVAC control module or powertrain control module is detecting a higher than expected voltage on the A/C request input circuit. The fault is typically related to a shorted circuit, a stuck or faulty A/C request signal source, a poor connection, or a control module input fault. Confirm the exact symptoms, freeze frame data, and any related codes before proceeding.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
Diagnosis requires circuit testing with a digital multimeter or scan tool and basic understanding of control circuit behavior. Repairs are usually limited to wiring, connectors, or a switch or module replacement. Access to the wiring and components may vary by model year and should be verified by the technician.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify battery voltage and charging system output are within specification using a digital multimeter at the battery terminals, confirming a stable 12.6V key-off and proper charging voltage with the engine running.
- Review freeze frame data and record current and history DTCs before clearing any codes, noting whether the A/C request high voltage fault is intermittent or continuously active.
- Visually inspect the A/C request circuit wiring for chafing, pinched harnesses, or heat damage, paying close attention to areas near the firewall grommet, engine harness routing points, and any locations where the harness contacts moving components or sharp edges.
- Inspect connectors at the HVAC control head, body control module (BCM), and powertrain control module (PCM) for corrosion, bent terminals, or loose fit, as the A/C request signal is typically routed from the HVAC control head through the BCM to the PCM on most Chrysler, Dodge, Jeep, and RAM platforms.
- Check for aftermarket accessories, remote start installations, or recent electrical repairs that may have introduced an unintended voltage source onto the signal circuit.
- Confirm the location of the A/C request input and related components by referencing the factory wiring diagram for the specific model and powertrain, as the HVAC control head, BCM, and PCM connector locations vary between platforms; do not assume a universal pin location without verifying the correct factory diagram for the exact vehicle in the bay.
Step 2: Diagnostic Verification
- Use a scan tool to monitor the A/C request signal state (on/off or voltage state) with the key on, engine off and then with the engine running, comparing the displayed state to actual A/C switch operation on the control head.
- Measure the A/C request circuit voltage at the control module connector with the circuit connected and then with it disconnected, comparing the reading to the expected low-reference or switched voltage state defined by the factory service manual for the exact circuit identified in the wiring diagram.
- Perform a circuit continuity and short-to-voltage test on the signal wire against chassis ground and against battery voltage using a digital multimeter, verifying there is no unintended continuity or voltage bleed from an adjacent circuit in the connector or harness.
- Check the A/C request switch or HVAC control head operation through its full range (off, low, high, auto modes) and confirm the output signal changes states as expected with each switch position.
- Verify the ground circuit integrity between the affected component and the chassis or module ground using a voltage drop test, confirming less than 0.2V drop under load between the component ground and chassis ground point.
- Isolate the fault by disconnecting the suspect component (HVAC control head or A/C switch) and rechecking voltage at the control module. If voltage remains high with the component disconnected, the fault lies in the wiring harness or the control module itself rather than the switch.
Step 3: Resolution & Reset Process
- Repair or replace the damaged wiring, connector, or faulty component based on confirmed test results, using OEM-spec wiring and weatherproof connectors or terminals where applicable.
- Replace the control module only after all wiring and component checks have been completed and documented, since Chrysler PCM and BCM replacements typically require module programming through a factory-level scan tool.
- Clear all stored DTCs using the scan tool after the repair is complete.
- Perform a complete system reset and any required module relearn, VIN configuration, or security SKIM/SKREEM synchronization procedures per factory service information if a PCM or BCM was replaced.
- Road test the vehicle and operate the A/C system through all modes (max A/C, auto, defrost with A/C compressor engagement) to confirm the fault does not return and that the compressor clutch engages correctly.
- Recheck for stored or pending codes after the test drive using the scan tool and document the final results along with a completed freeze frame comparison.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- Diagnostic scan tool with full HVAC, BCM, and PCM bi-directional access (factory-level tool such as Chrysler’s wiTECH preferred for accurate live data and module programming)
- Digital multimeter and factory wiring diagrams specific to the exact model, year, and powertrain combination
- Repair parts as needed: wiring pigtail or harness section, weatherproof connector terminals, HVAC control head or A/C request switch, BCM or PCM if confirmed faulty through isolation testing
- Factory programming or software update via wiTECH, required any time a BCM or PCM is replaced on Chrysler platforms
Average Component Price:
- Wiring and connector repair (pigtail, terminals, loom repair): $40–$150 in parts
- HVAC control head or A/C request switch: $120–$450 depending on whether the vehicle uses a basic manual control head or an automatic climate control touchscreen unit
- BCM replacement: $250–$600 part cost before programming
- PCM replacement: $500–$1,200 part cost before programming, highly dependent on engine and trim level
- Dealer or independent shop programming/software service: $100–$250 per module, often billed as flat-rate or per half-hour of programming time
Estimated Labor Hours:
- Diagnostic time: 0.8–1.5 hours for circuit testing, scan tool verification, and fault isolation
- Wiring or connector repair: 0.5–1.5 hours depending on harness accessibility and location of the damaged section
- HVAC control head or switch replacement: 0.5–1.2 hours depending on dash trim removal requirements
- Module replacement and programming, if required: 1.0–2.5 hours combined for R&R and factory programming/configuration
- Verification and road test: 0.3–0.5 hours