# AC System Temperature Sensor Repair in Upland > Auto climate blowing the wrong temperature? Route 66 Auto Repair in Upland tests outside, cabin and sun load sensors before replacing any AC parts. Source: https://route66autorepairshop.com/cooling-heating-ac-services/ac-system-temperature-sensor-repair Updated: 2026-09-17 Business: Route 66 Auto Repair, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699 Hours: Monday to Friday 8 AM–5 PM, Saturday 8 AM–2 PM, Sunday closed **TLDR:** Auto climate trusts its **temperature sensors**. When one lies, the system misbehaves. We compare each **sensor reading** to a real measurement. Automatic climate control depends on temperature sensors: one outside, one in the cabin, and often a sun load sensor on the dash. Route 66 Auto Repair in Upland tests these sensors when auto mode blows hot when you want cold, or the dash shows the wrong outside temperature. A bad sensor can make a healthy AC act broken, so we check them before anything else is replaced. ## Which sensors does your AC rely on? The outside air sensor usually sits behind the grille. The in-car sensor often hides behind a small grille in the dash or headliner, with a tiny fan that draws cabin air across it. The sun load sensor sits on top of the dash near the windshield. The evaporator sensor, which prevents icing, is covered on [AC thermostat replacement](https://route66autorepairshop.com/cooling-heating-ac-services/ac-thermostat-replacement). The climate module blends these readings with your setting to decide fan speed, vent mode and how cold to run. One bad reading throws off the whole calculation. ## Signs a temperature sensor is failing - Dash shows an outside temperature that is far off - Auto mode blows hot air on a hot day - Fan runs on high constantly in auto mode - Temperature swings without a setting change - A buzzing or silent in-car sensor fan ## Our sensor repair process 1. **Read the data:** We compare each sensor's reported value with a thermometer reading at the same spot. 2. **Check the circuit:** Wiring and connectors are tested for resistance and damage. 3. **Replace the sensor:** The faulty sensor or aspirator fan is replaced with the correct part. 4. **Verify auto mode:** Auto climate is tested for correct response on a road test. ## What's included in temperature sensor repair - Scan tool data comparison - Thermometer checks at each sensor - Wiring and connector tests - Sensor or aspirator fan as quoted - Auto climate road test ## Need-now or need-later? **Need now:** - Auto mode blowing heat that you cannot override in summer - Defrost not working correctly because of wrong data **Need later:** - Outside temperature display a few degrees off - A quiet in-car sensor fan with normal auto operation ## How pricing and timing work An outside sensor behind the grille is usually quick. An in-car sensor behind dash trim takes more time. Wiring faults can take longer to trace, and we update you before time grows. If the module itself is suspect, see [heater control module repair](https://route66autorepairshop.com/cooling-heating-ac-services/heater-control-module-repair). Wider electrical faults are handled with our [electrical system diagnostics](https://route66autorepairshop.com/electrical-services/electrical-system-diagnostics). If the sensors test good, the next step is an [AC system diagnostic](https://route66autorepairshop.com/cooling-heating-ac-services/ac-system-diagnostic). ## After the repair The outside temperature display may take a short drive to update. Keep the in-car sensor grille clear of stickers and dust. ## Frequently asked questions ### Why does my car say it is hotter outside than it is? The outside sensor can read engine heat when the car is parked or in traffic. If the reading stays off after driving, the sensor or wiring may be faulty. ### Can I use manual mode instead? Often, yes. Manual mode can bypass some sensor logic until the repair is done. ### Is this the same as the engine temperature sensor? No. The engine coolant sensor affects engine temperature readings and fan control. These sensors are for cabin comfort. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.