Make a decision
Furnace cleaning versus repair
One scope
Cleaning removes material from a named accessible surface.
The other scope
Repair corrects a diagnosed failed component, leak or installation defect.
A concrete example
A water leak from a cracked pan will reappear after a cabinet wipe. Cleaning can remove the spill, but the repair must correct the source and verify drainage.
Which question settles it?
If heat is intermittent or an alarm sounds, ask for fault diagnosis before a cleaning purchase.