🚨 Diagnostic Profile
Vehicle Make: Chrysler
Description: A/C Evaporator Temperature Sensor Circuit Low Voltage. The evaporator temperature sensor (typically a negative temperature coefficient thermistor) reports cabin evaporator core temperature to the HVAC/climate control module or PCM. A low voltage condition indicates the sensor signal is reading below the expected range, which may point to a shorted sensor, a shorted signal circuit, a poor ground, or a module fault.
🚨 Repair Difficulty Tier
Tier: [DIY / Beginner]
Diagnosis requires a digital multimeter and basic electrical testing. Sensor replacement is commonly accessible but may require removal of interior panels or HVAC housing components depending on the model year. Circuit repairs involving wiring harness or module work may elevate this to [Intermediate] or [Professional Only].
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Verify battery voltage reads approximately 12.4–12.6V at rest and that charging system output falls within the standard 13.5–14.7V range at idle with accessories off, using a digital multimeter at the battery terminals.
- Scan all modules (PCM, BCM, and HVAC/climate control module) for stored and pending DTCs and record freeze frame data, including the exact evaporator temperature reading captured at the time the code set.
- Visually inspect the evaporator temperature sensor connector, typically located on the evaporator core housing behind the dash or glovebox assembly, for corrosion, bent pins, moisture intrusion, or loose seating.
- Inspect the sensor wiring harness for chafing, pinched sections, or heat damage along its routing path from the HVAC housing to the control module.
- Check related chassis and HVAC module ground points for corrosion, looseness, or high resistance using a voltage drop test under load.
Step 2: Diagnostic Verification
- Disconnect the sensor and measure resistance across the sensor terminals with an ohmmeter; compare the reading against the manufacturer’s temperature-resistance chart for that specific NTC sensor (resistance should decrease as temperature increases, consistent with standard NTC thermistor behavior).
- With the sensor disconnected, measure the signal circuit for shorts to ground (continuity to chassis ground should read open/infinite resistance) using a digital multimeter, referencing the applicable Chrysler wiring diagram for the exact harness routing and connector pinout.
- Key on, engine off, measure reference voltage at the sensor harness connector (most Chrysler evaporator temp circuits use a 5V reference signal) and confirm a solid ground return using a digital multimeter against a known good chassis ground.
- Confirm sensor reading on the scan tool with the connector disconnected (voltage/temperature should default toward an out-of-range extreme) and reconnected (reading should return to a plausible ambient/cabin temperature) to isolate sensor versus circuit faults.
- Test the HVAC control module or PCM internal circuitry only after all external circuit and sensor tests pass, as module-level faults on this circuit are uncommon relative to sensor and wiring failures.
Step 3: Resolution & Reset Process
- Repair any damaged wiring, corroded connectors, or poor grounds identified during verification using proper soldered, heat-shrink splice connections or OEM pigtail repair kits; avoid crimp-only butt connectors in engine bay or HVAC moisture-exposed areas.
- Replace the evaporator temperature sensor if it fails resistance testing or does not match the temperature-resistance specification curve; access typically requires partial HVAC housing or evaporator core cover disassembly depending on platform.
- Clear all stored DTCs using a capable scan tool and perform a full module re-scan to confirm no immediate code return.
- Perform a complete A/C system operational test, confirming climate control response, blend door actuation, and sensor reading accuracy and stability at idle and under load (increased engine RPM/compressor cycling).
- Road test the vehicle through multiple A/C compressor cycling events and rescan for any returning or pending codes before releasing the vehicle.
📦 Parts, Labor, and Budget Estimates
Required Components/Software:
- Evaporator temperature sensor (OEM or OEM-equivalent NTC thermistor sensor specific to the exact Chrysler model/year/platform — verify fitment by VIN at a dealer parts counter or trusted parts supplier)
- Connector repair kit or replacement pigtail harness connector, if corrosion or damage is found
- Dielectric grease and electrical contact cleaner
- Factory-level scan tool (e.g., Chrysler wiTECH or equivalent OEM-capable scan tool) for accurate DTC retrieval, live data streaming, and verification; aftermarket scan tools with manufacturer-specific enhanced data may suffice for basic diagnosis
Average Component Price:
- Evaporator temperature sensor: approximately $25–$75 (part cost only, varies by platform)
- Connector or wiring repair materials (pigtail, splice kit, heat-shrink connectors): approximately $15–$50
Estimated Labor Hours:
- Diagnostic time (code retrieval, circuit/sensor testing): 0.5–1.0 hour
- Sensor replacement (includes partial dash/HVAC housing access as needed): 0.5–2.0 hours depending on platform accessibility
- Wiring repair, if required: 0.5–1.5 hours depending on harness location and damage extent
- Verification, DTC clear, and road test: 0.3–0.5 hour
Total Estimated Cost Range (Parts + Labor, Shop Rate $120–$170/hr): Approximately $130–$450 for straightforward sensor replacement; $250–$600+ if wiring harness repair or extended diagnostic time is required.