Thermal Gauge

HVAC field app · works with no signal

Know what your gauges are telling you.

Superheat and subcool with a live verdict, P-T for seven refrigerants, airflow, psychrometrics and load calcs — plus Gary, an assistant who answers in shop talk. All of it runs on your phone, offline.

Open the web app See the tools

Free web app for any phone or computer. Android app available. No account, no sign-in.

Thermal Gauge superheat and subcool results with a Charge OK verdict
Thermal Gauge P-T chart showing R-410A at 40 °F is 118.8 psig

Actual screens from the app

The tools

Everything you'd pull out of the truck, on one screen.

Each tool opens from the menu, remembers what you typed, and switches between °F and °C with every temperature in the app.

Ask Gary

An assistant that talks like a tech.

Gary works with no internet and no account. Type or say what you're seeing — readings, symptoms, slang, typos — and he tells you what it means and where to start. Every answer comes from the app's built-in reference, so it works in a basement with no bars.

head 450 suction 130 liquid 105 outdoor 95 — what's wrong? 24 volts across the float switch how do I change out a compressor gas pack won't heat 9 gpm 10 degree rise on a 3 ton can I use a 440 cap instead of 370
Gary reading a full set of R-410A gauge readings and naming the likely problem
Gary giving step-by-step compressor change-out instructions
Readings

Pressures & charge

Reads a whole set of gauge readings, works out superheat and subcool, and gives normal pressures for today's outdoor temperature.

47 cards

Troubleshooting

Symptom to cause with a "start here" step: frozen coils, short cycling, lockouts, noises and smells.

24 V & line voltage

Meter readings

"0 V between Y and C at the condenser" — he tells you which switch is open and what to check next.

21 guides

Component change-outs

Compressors, evaporator coil pulls, heat strips, blower motors, gas valves, igniters — what to match and every step.

New

Package units & water-source

Gas packs, rooftop units, belts, draw-through traps, WSHP lockouts, water flow and 500 × GPM × ΔT.

On the phone

Data tags from a photo

Snap a nameplate or gauges and Gary reads them — model, serial date and refrigerant. Photos never leave the phone.

Student Mode

Built for the classroom and the trainer.

Turn on Student Mode in Settings and two tabs appear: Faults, 40 troubleshooting exercises in four tiers, and How To, step-by-step guides for the skills every new tech needs.

Beginner
B-01 · 10 faultsThe AC isn't coming on at all.

Look, listen and check the basics. Few or no tools.

Apprentice
A-05 · 10 faultsThe furnace starts making noise but never lights.

Meter work: find the part that stopped the call or the power.

Journeyman
J-03 · 10 faultsWhen I turn the fan to ON, the outside unit starts too.

Gauges, temperatures, amps and line voltage together.

Expert Tech
E-02 · 10 faultsPoor cooling, and the small copper line outside feels oddly cold.

Subtle and combined faults. Readings have to be interpreted, not just read.

Set safely. Every fault is set by an instructor with the power locked out, using entry-level tools. None of them vent refrigerant, open gas piping or bypass a safety — and each one has run-time and stop limits. An instructor view shows the setup; students get three hints, then the answer.

How To guide showing a ladder wiring diagram of a split AC

28 How To guides, including

  • Read a wiring diagram
  • Check for voltage
  • Lockout / tagout
  • Braze copper
  • Make a flare
  • Charge refrigerant
  • Recover refrigerant
  • Pressure test & evacuate
  • Check gas pressure
  • Clean coils
  • Water-source heat pumps
  • Adjust a blower belt

Themes

Make it yours. Six looks, one tap.

Pick a theme in Settings. The app icon and the shield stay the same whichever you choose.

Default theme
Default
Light Mode theme
Light Mode
Dark Mode theme
Dark Mode
Coastal theme
Coastal
Live Wire theme
Live Wire
Fire and Ice theme
Fire and Ice

Built for the field

Attic, crawlspace, rooftop — no signal needed.

Fully offline

Every calculator, chart, guide and Gary answer is stored on the phone. Nothing waits on a connection.

Private

No account to create. Photos of data tags and gauges are read on the phone and never uploaded.

Service notes

Save notes with photos and labels for each job, and copy them into a text or email in one tap.

Voice both ways

Ask Gary with the mic when your hands are dirty, and have him read the answer out loud.

Get Thermal Gauge

On your phone in a minute.

Web app

Any phone or computer

Open it in your browser. It keeps working offline after the first visit.

Open the web app

Home screen

Install it like an app

iPhone: Share → Add to Home Screen.
Android: browser menu ⋮ → Install app.

Android app

Want the installer?

Ask for the Android app, or send feedback and feature requests.

Contact us

Field reference only. Always follow the equipment manufacturer's instructions and local codes.