Technical directory · Buying
Written diagnosis versus cleaning
Noise, weak heat and shutdown are symptoms; dust may be present without causing them.
What to observe
Ask what observation or measurement connects the proposed cleaning to the complaint.
A field example
A furnace that short cycles after several minutes needs a reasoned test sequence. Finding dust during a visit does not establish that the dust caused the shutdown.
What the written work should say
A diagnosis should identify likely cause, next test and any repair authorization separately from cleaning.
Where this task stops
If a cleaning is sold as a guaranteed cure for an unexplained safety or electrical fault, seek a second opinion.