SYMPTOM · HVAC + REFRIGERATION · ORANGE COUNTY

Thermostat not responding.

Blank screen, frozen display, or HVAC won't respond to commands. We trace the 24V circuit from stat to board in 30–60 minutes and quote in writing.

(949) 992-8840
30–60 min typical
Same & next-day Mon–Sun
Residential & commercial

Common causes for this symptom.

  • Dead batteries (smart thermostats).

    Most "smart" thermostats still ship with backup AAs that quietly die after 12–18 months — the screen goes dark or flashes a low-battery icon and the system stops responding to schedule changes.

  • C-wire / low-voltage wiring break.

    Common after a DIY smart-thermostat install. Without a continuous 24V common, the new stat browns out or reboots in a loop. We trace the run, splice or pull a C-wire, and test all modes before we leave.

  • Control board fault at the air handler.

    The thermostat is fine — the control board on the furnace or air handler is not responding to Y/W/G calls. Voltage and continuity tests at the board confirm it. Most boards are stocked and replaceable same-visit.

  • Sensor mismatch or location issue.

    The thermostat is reading a stratified pocket of air (near a return, in a hallway, by a sunny window) and short-cycling the system. Adding a remote sensor or relocating the stat fixes it without replacement.

What to expect when we arrive.

  • CSLB License #1128756 — California state contractor.

  • EPA Section 608 certified for refrigerant handling.

  • Written quote before any work — no on-the-fly upsells.

  • OEM parts on every job. 90-day warranty on parts and labor.

Three steps. No surprises.

  1. Book in 2 minutes.

    Pick your symptom and a time window. We confirm by text.

  2. Diagnose in 60 minutes.

    We arrive in a marked van, diagnose the issue, and quote the repair before we touch a screw. $65 diagnostic fee — waived if you say yes to the repair.

  3. Fix it today, when we can.

    80% of repairs finish in the same visit. Every job carries a 3-month warranty (6–12 months on compressor work).

About Trust AC →

Other symptoms we diagnose.

What your neighbors said.

5.0 stars · 8 reviews on Yelp →

  • I first found Ivan almost 9 years ago, when he had just started his business. He was prompt, knowledgeable and able to fix every type of appliance. He became my go-to guy for any issues. He is responsive, comes on time, reasonable rates, and gets the job done efficiently and properly, the first time. His specialty is Air Conditioning, which gets a lot of use in Orange County summers — call Trust AC Repair!

    — JoLee G.

    Yelp · Verified

  • I love when a business truly earns a five-star review. Rest assured that Trust AC Repair is one of those select few. From calling to schedule an appointment, to showing up on time, to being trustworthy when advising on what needs to be done, to making repairs — this is an A+ business all the way through. Ivan, the owner, does not upsell to make a buck. He is professional, knowledgeable, and experienced.

    — Jennifer S.

    Yelp · Verified

  • Ivan is great. I appreciate his methodical, step-by-step approach to figuring out the problem and finding solutions. Communication is clear — he called me approximately 30 minutes before arriving, and cleaned up after the job was done. Thank you Ivan for being our go-to repair person.

    — Chiara K.

    Yelp · Verified

Thermostat dead? We're often out same day.

Most thermostat calls finish in under an hour. We quote in writing before any work.

Or call (949) 992-8840