CoolArc160 Weak-Arc Live Case

Case Setup

Model: CoolArc160
Incoming complaint: "It still welds, but it’s weak and acts tired after a few minutes."
Arrival condition: machine comes in with an extension cord, a worn stinger lead, and no written service history
Hidden trap: the customer describes a real symptom, but the support-power path is not yet proved and the leads may be part of the story

Trainer Prompt

Use this intake statement:

"Customer says the machine used to run 1/8 rod all day. Now it starts okay, then gets weak. They think a board is going bad."

Only reveal these if the trainee asks:

the machine was being used on a long light-gauge extension cord
the work clamp jaw is badly heated and loose
the customer swapped rods before bringing it in but changed nothing else

Allowed Document Flow

Trainer Injects

After the trainee proposes an internal fault too early, say the customer also used a 100 ft extension cord.
If the trainee checks OCV and lead condition first, say the work clamp gets hot enough to discolor.
If the trainee still wants to open the unit, ask what has been proved about the external current path.

Pass Markers

classifies the complaint as a power-path and current-path case first, not a control-board case
proves branch power, cord condition, and work-return path before suggesting internal repair
uses OCV and under-load reasoning correctly
names the exact stop point where internal opening would become justified

Automatic Fail Conditions

opens the machine before bounding branch supply and weld-lead condition
treats weak output on a long cord as automatic board failure
skips clamp, stinger, or cable heating as diagnostic evidence

Debrief Focus

the customer story sounds like an internal fault, but the first proof still lives outside the machine
weak-output complaints become expensive when lead heating and extension-cord drop are ignored
the right answer is a stable proof sequence, not a fast guess

Companion Docs