If you fix things for a living

Where being wrong is physical

Trades, field service, maintenance, IT support, agriculture, engineering technicians. What separates this work from every other trade in this block is that a wrong answer has a physical consequence and often an immediate one.

A wrong adjective in a marketing email is embarrassing. A wrong torque figure is a wheel coming off. That difference sets everything else in this lesson.

The rule that overrides everything

The manufacturer's documentation for that exact model is the authority. Always.

Torque settings, clearances, wiring colours, refrigerant charge, pressure ratings, chemical dilutions, fuse ratings, firmware versions, part numbers. Every one of these will be produced confidently by a model, in the correct format, from a distribution of similar values across similar equipment. That is not a lookup. There is no manual inside it.

Get the manual — most manufacturers publish PDFs, and the earlier lesson on extraction gets the text out exactly — and then, if you like, ask the model questions about the manual you attached. That is the safe configuration, and it turns a 300-page service document into something you can query on site.

Where it genuinely helps

• Interpreting an error code with the manual attached. Fast, accurate, and exactly the sourced configuration.
• Diagnosis as a conversation. "Symptoms are these, I have checked these four things, what have I not considered?" You supply the observations; it returns candidates you go and test. This is a genuinely valuable use, because a list of hypotheses is not a diagnosis and everybody in this trade already knows the difference.
• The job report and the quotation. Dictate on the way back to the van, get a structured report out, check the figures.
• Explaining the fault to the customer in plain language, without condescension, from your own diagnosis.
• Turning a photograph of a nameplate into a searchable model and serial number — then verify against the supplier's catalogue.
• Translating a manual that only exists in the manufacturer's language.
• Building a checklist from a procedure document you attached.

Where it is dangerous

Part numbers. A plausible part number that does not exist wastes a day. One that exists but is wrong for this machine can be worse. Always cross-check against the supplier's catalogue.

Safety-critical procedures. Gas, electrical, lifting equipment, pressure systems, aviation, food handling. These are governed by certification schemes and regulations that specify competence and, usually, the source of the procedure. A generated procedure is not a procedure, and following one does not satisfy a scheme that requires the manufacturer's or the standard's method.

Equipment it has barely seen. Models are trained mostly on consumer-facing text. They know a great deal about a common domestic boiler and very little about the specific industrial machine you maintain. The register of confidence does not change between those two cases, which is what makes it dangerous — it will answer about your unusual kit exactly as fluently as about a washing machine.

Photos from the field

Good uses: a nameplate, an error display, visible damage, a wiring layout you want a second opinion on.

The caveats from the images lesson apply and are worse in a plant room: glare on a display, poor light, a dirty label. Wipe it, get close, take three from different angles. And crop before sending — the frame may contain a customer's premises, a person, or a document on a bench.

The record protects you

The customer says the fault was there before. The insurer asks what condition it was in. A dispute arrives eighteen months later.

Photographs before and after, a written report produced the same day, the readings you took, the parts you fitted with their numbers. Dictating that report in the van and having it structured immediately is the difference between a record that exists and one that does not, and it is one of the strongest arguments for these tools in this trade.

Working without a signal

Half this work happens in basements, plant rooms, fields and lifts. A cloud service is unavailable exactly where you need it.

A local model on a laptop in the van works with no signal at all — Ollama with a small model, plus the manuals stored locally as PDFs. It is slower and it is weaker, and it is available, which beats a better model that cannot be reached. For anyone whose working day includes places with no coverage, this is not the fallback option. It is the main one.