Deterministic fault diagnosis.
Zero guesswork.
A professional field web app that ranks supported fault patterns from the manual gauge readings you enter. No proprietary probes required. After it is installed or loaded, the engine and calculators can be used without a signal.
Most diagnostic apps guess. This one shows its work.
Three maybes and a shrug
Every other app throws three possible faults on the screen with no explanation and expects you to pick one. That's not a diagnosis — that's a coin flip with extra steps.
An AI answer you can't audit
AI-first diagnosis can produce an answer without exposing a repeatable chain of indicators you can check and defend. Determinari keeps AI on assistance work and keeps the fault call deterministic.
PT charts in a glovebox, math in your head
The tools that don't guess instead make you do everything by hand. Lookup. Interpolate. Subtract. Re-check. On a 100°F rooftop with a customer waiting.
The Diagnostic Pro difference
Deterministic weighted rule matching
A weighted rule-match engine — not an LLM or probability model — ranks the supported fault patterns from the readings you enter. The same inputs produce the same ranked result, with the matching indicators shown beside it.
Pre-check gate before any reading
The app blocks the diagnosis until airflow, coil, blower, and stabilization are confirmed. Bad readings in, bad faults out. We won't let you.
Built around your hands
Glove-friendly tap targets. Industrial dark UI. Big numbers, no fluff. Once the app is installed or loaded, the engine and calculators remain usable without a signal. Designed for the truck, not the office.
Other tools stop short. Determinari finishes the diagnosis.
We don’t name names — but you already know the categories. Here’s where each one leaves you, and where Determinari keeps going.
Probe-locked apps
Gate the real value behind $300+ wireless probes. No probe synced, no diagnosis — and a dead Bluetooth link can stall the whole call.
Determinari: Enter manual readings from the gauges and instruments you use — no proprietary probe pairing required. Verify that the readings and instruments are appropriate for the job.
AI-first diagnosis apps
A model-generated answer may not expose a repeatable chain of indicators you can audit or defend, even when the model can read live measurements.
Determinari: A deterministic weighted rule-match engine shows the indicators behind each ranked result. AI assists with plate reading, manual discovery, and optional follow-up explanation — never the fault call.
PT-chart calculators
Give you superheat and subcooling, then stop. You still interpret the fault in your head on a hot rooftop with a customer waiting.
Determinari: Carries the reading all the way to a ranked, evidence-backed fault — and the next verification step to confirm it.
Back-office field-service software
Built for dispatch, invoicing, and the office. Powerful for the calendar, but there's no diagnostic brain in the truck.
Determinari: The diagnostic layer those tools lack. Runs right alongside them — focused on the call, not the schedule.
Proof for the tech. Consistency for the owner.
For technicians
Move from readings to a ranked, explainable result without waiting on proprietary hardware. See the matched indicators, verify the next differentiating test, and walk back to the customer confident in the call.
For shop owners
Standardize how the crew captures evidence, track callback costs, compare shop performance, and coach from real jobs. Fewer avoidable return visits and more consistent closeouts are the operating return on every paid seat.
Five senses, in the right order
Before you read a single pressure, the app walks you through the checks a senior tech would do on instinct.
Pre-check gate
Before any pressure gets entered, the app walks you through visual inspection, airflow, coil cleanliness, filter, blower, and stabilization. Skip a step and the diagnosis button stays disabled. The cheap stuff hides expensive symptoms — this catches them first.
Live SH / SC engine
Nine refrigerant libraries — R-410A, R-22, R-32, R-454B, R-134a, R-404A, R-407C, R-422B, R-507A — with linear interpolation. Punch in your pressures and temps; superheat, subcooling, and saturation temps update live as you type. A2L refrigerants are flagged automatically.
Ranked rule matches, with the reasoning
A deterministic weighted rule-match engine ranks 11 supported fault models — from undercharge and overcharge to line restrictions, airflow problems, non-condensables, and heat-pump-specific faults like defrost and reversing-valve issues — plus normal operation. The score reflects matched indicators; it is not a probability or a guarantee. Each result shows its indicators so you can verify the call.
3D equipment explorer with live refrigerant flow
Walk around a condensing unit, furnace + air handler, mini-split, packaged rooftop unit, and heat-recovery VRF system — right in the app. Tap any part to open its entry in the 115-part component library — what it does, how to test it, what failure looks like. The commercial scenes go deep: tandem compressor racks with independent circuits, VFD-driven blowers, economizer hoods, branch selector boxes, and the sensor checks that separate a real compressor failure from a bad transducer reading. Turn on flow mode to watch refrigerant run the circuit in cooling or heating, high side and low side color-coded with the refrigerant's state called out at each stage. And when the engine ranks a fault, "See it in the unit" jumps straight to the suspect part in 3D.
Senior Tech explanation
Each supported diagnostic result includes a plain-language explanation of the engine's matched indicators: airflow first, then the evaporator, condenser, and what the readings say together. It is generated from the same deterministic rules as the ranking and is available after the app has loaded. Use it to guide verification, not as a substitute for technician judgment.
Follow-up questions, answered
When the built-in explanation isn't enough, ask. An optional AI follow-up chat answers questions about the engine's call — what to verify first, how the repair usually goes — with manual citations badged by source, OEM or third-party. It never re-diagnoses: the deterministic ranking is the verdict, and the chat's only job is to walk you through it.
Symptom matrix & quick calcs
A printable, glove-friendly cheat sheet of every common fault signature on every refrigerant. Quick calcs for target superheat (TXV vs. fixed orifice), capacity, delta-T, and rule-of-thumb sanity checks. The reference card you wish was in the truck.
Plate camera & parts sourcing
Snap a photo of the data plate to capture model and serial details, then pin a verified OEM parts manual before searching. Supplier search can open matching searches across the configured supplier sources; some integrations may return live results when the supplier connection and account support them, while others open the supplier's search page. Confirm fit, price, and availability with the supplier.
Owner-built workflows
Shop owners can author custom, step-by-step workflows — startup checklists, PM routines, and brand-specific procedures — for their team. Connectivity is required to save, distribute, and retrieve cloud workflow data.
Owner analytics & callback costs
Role-aware dashboards, job filters, technician coaching insights, callback-cost tracking, and CSV exports give owners a consistent view across the shop. Use the evidence to find repeat work, coach from real calls, and benchmark performance without taking the tools out of the technician's hands.
EPA-oriented records & reports
Track refrigerant activity and cylinders, export EPA-oriented records, and configure scheduled compliance reports. With refrigerant tracking requirements tightening and A2L equipment becoming the factory norm, structured records matter now. Always confirm the rules that apply to your equipment and jurisdiction.
Service reports, customer-ready
Generate a printable service report in plain language for recorded job information, checks, findings, and repairs. Saving cloud records and generating or sharing reports requires connectivity.
Offline-capable engine
Basements. Rooftops. Equipment rooms. After the app is installed or loaded, the diagnostic engine and calculators can be used without a signal. Cloud job saves, reporting, supplier searches, and synchronization require connectivity; do not rely on offline work being saved or synced automatically.
Published references, where shown.
Some guides and screens identify published references for the topic at hand. These topic areas may be useful starting points, but the app does not make every result traceable to a standard. Confirm the applicable manufacturer instructions, codes, and standards for the equipment and jurisdiction.
The refrigerant transition is here. The app already speaks it.
As the industry moves to next-generation A2L refrigerants, every tech is suddenly charging and troubleshooting systems they've never touched. The PT numbers are different. The handling rules are different.
Determinari shipped R-32 and R-454B from day one — full PT libraries with linear interpolation, the same deterministic SH/SC engine, and the ASHRAE A2L class flagged automatically wherever it appears. No add-on, no update to wait for, no relearning the tool.
Walk up to an A2L system with the same certainty you have on R-410A.
The timing matters beyond charging: in 2026, EPA refrigerant-tracking expectations are tightening as A2L equipment becomes the factory norm. Determinari's refrigerant and cylinder records, EPA-oriented exports, and scheduled compliance reports help shops build a defensible trail. Confirm the rules for each system and jurisdiction.
Flagged as A2L (mildly flammable) automatically throughout the app — so the safety class is in front of you before you connect a hose, not buried in a spec sheet.
Nine refrigerants, named.
Every refrigerant the SH/SC engine computes — spanning legacy, current, and next-gen A2L — each with linear interpolation and its ASHRAE safety class flagged.
Every seat. Every feature. Every refrigerant.
No paywalled fault models. No "pro tier" for the math.
Prove it once. Then equip the shop.
Each shop gets one real diagnosis, one linked verification, and one customer report with no timer. Continued access is $29 per billable seat each month or $290 per billable seat each year, with checkout and subscription management through Whop. Owners are not billable seats. The PT chart and SH/SC calculators are free for everyone.
Monthly
- Full diagnostic engine
- Installable — works offline
- All 9 refrigerant libraries
- Owners are not billable seats
- Cancel anytime
Annual
- Everything in monthly
- Priority support
- Annual price locked
- Owners are not billable seats
Frequently asked questions
Diagnose it. Don't guess it.
Run one real workflow first. Then unlock every feature, refrigerant, and update for $29 per billable seat monthly or $290 per billable seat yearly through Whop.
Not ready to subscribe? Try the math first.
Free PT chart lookups and superheat/subcooling calculators — the same libraries the engine runs on.