EATC Temperature Selector Circuit Failure
The C1780 code is a manufacturer-specific diagnostic trouble code indicating a fault in the temperature selector circuit of the automatic climate control system. The control module detects that the signal from the temperature selector is out of its calibrated range, intermittent, or does not match the user's command position. This prevents the HVAC system from properly adjusting the blend of hot and cold air to achieve the desired cabin temperature.
1. Commonly Affected Makes
2. Most Common Causes
- Faulty climate control module (EATC/CCM)
- Worn or defective temperature selector switch or potentiometer
- Open circuit, short to ground, or short to voltage in the selector wiring
- Loose, corroded, or damaged connectors or pins in the HVAC panel circuit
- Blown fuse or poor power/ground supply to the control module
3. Symptoms You Will Notice
- Inability to adjust cabin temperature
- HVAC system blows only hot or only cold air regardless of setting
4. Step-by-Step Diagnosis
Check for blown fuses and verify proper power and ground at the climate control module.
Inspect the temperature selector switch and its wiring for damage, corrosion, or loose connections.
Test the selector switch resistance or voltage signal per manufacturer specifications.
If wiring and switch are okay, suspect a faulty climate control module.
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, the vehicle remains drivable. However, you may lose the ability to control cabin temperature, which can affect comfort and defogging performance.
How much does it cost to fix?▼
Repair costs typically range from $100 to $400, depending on whether the issue is a simple wiring repair, a switch replacement, or a control module replacement.