Ask Marcel,
the largest HVAC troubleshooting database.
400,000 error codes, sourced from manufacturer manuals, with the page. In your pocket, in your browser, or plugged behind your tools.
Also on
- Manufacturer-sourced answers
- 126 brands, one app
- Explicit abstention when the source is missing
WHERE DO YOU START?
Fix it now
Search an error code, get its meaning, its source and the match limit. No account needed.
Equip a team
After-sales, CMMS and distributor use cases: sourced answer, explicit abstention, integration scope and price.
Build it into a tool
REST v1/v2, MCP server and Diagnostic Guide Beta: pick a surface, make a first call, read the quotas.
One intelligence
One HVAC brain. Three ways to use it.
Wherever you work — on site, at the desk, in the browser or in your own tools.
HVAC-Bench
We don't ask you to take our word for it.
Every answer is sourced from manufacturer documentation, with the manual reference — and measured on the HVAC-Bench.
See the proofCompatible with Claude, ChatGPT & Gemini — no affiliation
Mitsubishi Ecodan, Daikin Altherma, Toshiba, Gree — brands covered
Brands shown for information — corpus coverage, not partnership
Ask Marcel is an independent tool. F-Gas work must be carried out by a registered engineer. All brands belong to their respective owners.
The breakdown isn’t
the problem.
The real cost? The minutes wasted searching for the right info while the customer waits and your schedule falls apart.
Time lost per breakdown (scenario)
+30min
Hotline + doc search + hesitation
Hotline overloaded
Endless waiting while the customer watches.
Missing PDFs
12 folders, 47 manuals — and the right page stays hidden.
Return visit
Wrong diagnosis = second trip, margin goes up in smoke.
"The customer is watching. The hotline puts me on hold. I lose credibility in real time."
There’s a better way
Marcel suggests,
you decide.
One case, verifiable end to end — not three unrelated screens stitched together.
AI Vision: scan the nameplate.
Photograph the nameplate. Marcel reads the reference and matches it against the corpus: on this job, WH-UD09LE5.
REFERENCE READ FROM THE NAMEPLATE
PANASONIC WH-UD09LE5
A sourced answer, not a guess.
Marcel does not invent answers. It searches the AskMarcel base (400,000 error codes, 126 brands, 905 models) and returns the manual page that applies to the resolved reference.
CORPUS SEARCH
400,000 codes · 126 brands · 905 models
APPLICABLE SOURCE:
Panasonic J-Series manual — page 184
— code H72, reference WH-UD09LE5 resolved
The action, the value, the limit.
The check to perform, in order, when the source applies. If no exact page matches, Marcel says so instead of suggesting a random part.
SAME JOB, START TO FINISH
Check the sensor and its connector
Check the board (PCB) before ordering
Part
No reference imposed without an exact page
Why Marcel, not ChatGPT?
Built for the field, not for hype.
General-purpose AIs hallucinate. Marcel searches a verified document base and gives you the exact source: page, section, value.
Heat pumps
Daikin, Atlantic, Mitsubishi...
Air conditioning
Toshiba, Fujitsu, LG...
Boilers
Viessmann, Saunier Duval, Frisquet...
Stoves & pellets
Palazzetti, MCZ, ÖkoFEN...
Equipping a team?
Your service desk already answers. Make it answer right.
The same knowledge covering 400,000+ error codes, plugged behind your bot, your store or your CMMS — no rebuild.
HVAC diagnostic API
Sourced REST and MCP infrastructure — manufacturer citations, abstention, Developer key.
Learn moreUse cases by buyer
CMMS, AI agents, automated support, error-code lookup — dedicated pages per buyer.
Learn moreProof before the quote
HVAC-Bench and corpus: measured answers, not marketing promises.
Learn moreOne job.
Two realities.
Same breakdown, same technician, same customer. Only the tool changes.
ILLUSTRATIVE SCENARIO
This timeline is a demonstration, not a measurement. No field data is published yet, so we do not show it as an average.
Without Marcel
Traditional workflow
1h45
Total time
Arrive on site
Error code E7 displayed
Call manufacturer hotline...
Still waiting...
Partial answer, not sure
Searching PDFs...
Found it! (maybe)
Repair completed
With Marcel
With the AskMarcel database
20 min
Total time
Arrive on site
Error code E7 displayed
Photo → Marcel analyzes
Procedure + official source
Repair completed ✓
AskMarcel by the numbers
Error codes
Brands
Referenced models
Marcel Pro per month
Avoid one return visit = six months of subscription paid back.
Typical situations
Common situations, told without names and without review scores — not customer testimonials.
Anonymised illustrative cases. No first name, no verified review, no score: we do not publish a customer testimonial until it is traceable (source, date, consent).
Air-to-water heat pump, unknown code
The nameplate reference was found, the manual page opened, the sensor checked — without ordering a random part.
Pellet stove servicing
Service codes for the brands in the fleet are read from the phone, with no PDF to download.
Refrigeration call-out
The meaning of the code is read on site, instead of hunting through a 200-page manual.
Flue sizing
The calculation is done in front of the customer, which makes the technical case verifiable.
Gas boiler, intermittent fault
The diagnosis starts from the model's manual, not from a hunch.
SME after-sales team
Technicians rely on the same sourced answer, instead of three different methods.
A pro tool priced
like a screwdriver.
Marcel Pro — the HVAC assistant in your pocket. Simple, transparent, no commitment. Built for techs in the field.
Pro subscription
ex VAT
/ month
No commitment • Cancel in 1 click • €190 / year
Go Pro
For teams
A “fleet” plan for your technicians & service desk.
€15/seat/month, 3 seats minimum. Multi-user access, shared history, deploy in one day.
Frequently asked questions
Everything you need to know about Marcel to boost your productivity in the field.
Still have questions? Contact our support team
Knowledge base
Popular fault code guides
356AtlanticFault Code 356 Atlantic: insufficient water flow
Atlantic fault code 356: water flow below 10 l/min. Check valves, settings, flow meter wiring, circulation and bleeding (Atlantic FAQ).
U5Mitsubishi ElectricFault code U5 Mitsubishi Electric: causes, diagnosis and solution
Fault code U5 on Mitsubishi Electric heat pump? If air and fan checks are normal, replace thermistor TH8. For persistent failure, replace the outdoor power board.
H31PanasonicFault code H31 Panasonic: causes, diagnosis and solution
Panasonic fault code H31? After isolating the power supply, first correct any abnormal connection at connector CN204. If the connection is correct but the sensor resistance does not match the characteristic curve, replace the swimming pool sensor.
H64PanasonicPanasonic fault code H64: causes, diagnosis and solution
Panasonic fault code H64? If the connection is poor, correct it. If the voltage is 0 Vdc or 5 Vdc with no continuity, replace the outdoor high-pressure sensor.
F15PanasonicPanasonic fault code F15: causes, diagnosis and solution
Panasonic fault code F15? If supply or control voltage is missing, replace the outdoor unit PCB. If the return voltage is abnormal.
E1GreeFault Code E1 Gree: High Pressure — Causes and Repair
Gree E1 can indicate high-pressure protection on supported ranges. Check visible airflow obstructions and use the exact model manual before any repair.