HVAC Solar Radiation Sensor Circuit Malfunction
What does B1318 mean?
The B1318 code means the vehicle's onboard diagnostic system has detected: HVAC Solar Radiation Sensor Circuit Malfunction. This is a low severity code.
Common Symptoms
- Automatic climate control over-cools or under-cools
- AC system does not respond to sun exposure changes
- Climate control output inconsistent between sunny and cloudy conditions
- Solar sensor DTC stored in HVAC module
- Comfort level varies with sun position
Probable Causes (Ranked by Likelihood)
- Failed solar radiation sensor Very High
- Sensor blocked by dashboard objects or film High
- Corroded sensor connector Moderate
- Wiring fault to solar sensor Low
Step-by-Step Diagnostic Procedure
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Locate solar sensor on top of dashboard
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Check for obstructions blocking the sensor
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Read sensor output value with scan tool in sun and shade
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Inspect connector for damage or corrosion
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Measure sensor voltage output
Frequently Asked Questions
What is a solar radiation sensor?
It is a small light-sensitive sensor on the dashboard that measures sunlight intensity. The climate control system uses this data to compensate for solar heating of the cabin.
Where is the solar sensor located?
It is usually a small dome or disc on top of the dashboard near the base of the windshield, often near the defroster grille. Some vehicles have two sensors for left and right sun exposure.
Can I cover the sensor to improve cooling?
Covering the sensor will cause the climate control to think there is no sun and may reduce cooling effort. Leaving the sensor unobstructed allows the system to work as designed.