HVAC Fault Diagnosis

The tool supports all common HVAC system types including split systems, VRF/VRV, air handling units, chillers, boilers, heat pumps, fan coil units, rooftop units, package units, MVHR units, and DX cooling. The symptom-to-cause logic is system-aware, so you'll get different diagnostic suggestions for a split system tripping on HP than for a chiller showing the same symptom.

No. This tool provides AI-generated guidance to help structure the engineer's thinking — it doesn't replace site-based diagnosis by a qualified HVAC engineer. For anything involving refrigerants, gas, or high-voltage components, the qualified engineer's judgement (and the manufacturer's O&M manual) takes precedence over any AI suggestion.

This tool provides general HVAC troubleshooting guidance — useful when you need to think through a fault before the manual is to hand, or when you're working on equipment you don't have specific documentation for. PM Assist's main product lets you upload the actual O&M manual for your equipment and search it with AI for precise, source-cited answers to manufacturer-specific questions.

Yes, completely free with no signup required. The tool has reasonable per-session usage limits to keep it sustainable, but most engineers will not hit them in normal use. For unlimited use and an AI-searchable library of your actual O&M manuals, you can sign up for PM Assist.

Yes, but for the most specific refrigeration diagnostic we also publish a dedicated Chiller Diagnostic & Refrigerant Calculator that calculates superheat and subcool from real measurements and walks through the seven generic chiller fault categories (HP, LP, freeze stat, flow, oil, motor overload, short cycling). Use the chiller-specific tool when you have pressures and line temperatures; use this one for broader HVAC symptom-led diagnosis.

No. The text you enter is sent to the AI for the diagnosis and then discarded — it is not stored against an account, not used to train models, and not visible to anyone else. For an audit trail of past diagnoses, save or print the result, or use a PM Assist account where you control the retention and access policy explicitly.

Yes. The tool is a responsive web page that works on any device with a modern browser. Engineers commonly use it standing next to the faulty equipment on site, typing in the symptoms shown on the panel or BMS to get a structured diagnostic suggestion before opening the access panel.

General AI tools can give generic HVAC troubleshooting answers but they aren't grounded in HVAC engineering structure — they can hallucinate, mix up manufacturer-specific behaviour, or suggest unsafe procedures. This tool is built for HVAC fault structure, with prompts and result formats tuned to how engineers actually think about a fault (priority checks, likely causes, next diagnostic steps). The trade-off is breadth: for non-HVAC questions, a general AI is more flexible.

Not directly — manufacturer fault codes vary across Daikin, Carrier, Trane, York, Mitsubishi, Climaveneta and others, and OEM-specific code data isn't reproduced here for IP reasons. The tool's diagnostic structure covers the underlying conditions (e.g. "high discharge pressure") which are the same across manufacturers. Cross-reference the OEM code with the matching category, then use PM Assist on your actual O&M manual to retrieve the manufacturer's specific reset procedure.

Yes. The tool is stateless — anyone can use it from any device, no account, no shared session needed. Two engineers on the same site can independently run the same symptoms through it from their own phones if it helps cross-check the diagnostic logic.

If the symptom is genuinely unusual the tool may suggest several possibilities or recommend you consult the manufacturer's documentation. Use the symptom description field to include anything specific (recent works on site, BMS error codes, unusual sounds or smells) — more context produces a more accurate diagnostic. For deeply unusual faults, the right next step is PM Assist on the OEM manual rather than any general diagnostic tool.

Yes. PM Assist itself is the paid product — you upload your building's actual O&M manuals, drawings, certificates and commissioning records, and the full AI search runs against your specific documentation rather than generic HVAC knowledge. Free tools like this one are deliberately useful in their own right; the paid product is for FM teams who need source-cited answers from their own documentation.