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AskWhiz Playground

Real brands.
Real fault codes.
Prove you can diagnose it.

Free troubleshooting sim built from real service manuals.

Play now — no signupEPA 608 practice
Based on:Trane logoCarrier logoLennox logoGoodman logoRheem logo+72 more
Opened air-conditioner condenser unit showing fan, compressor and copper line set
Multimeter probes on a furnace control board

Mode 1 · Live

Diagnostic Challenge

Diagnose real faults using real fault codes, symptoms, and service data. 13 jobs on the board.

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Manifold gauge set and refrigerant recovery machine

Mode 2 · Live

EPA 608 Prep

Practice EPA 608-style questions written from the official topic outline, with CFR citations. Core & Type I, II, III.

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See where you rank

Top techs. Real scores. Climb the ranks.

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Apprentice

0 – 1,999 pts

Journeyman

2,000 – 4,999 pts

Senior Tech

5,000 – 9,999 pts

Master Tech

10,000+ pts

How it works

  1. 01

    Get dispatched

    A real fault on real equipment. The customer tells you what they noticed — if you ask.

  2. 02

    Work the system

    Switch units, inspect readings, compare against nominal ranges. The manual is your friend.

  3. 03

    Commit a diagnosis

    Wrong guesses cost points. Nail it and get the teach-back — what a pro checks first, with sources.

Built from 1,200+ real fault codes across 77 brands.

Real service manual data

Fault codes, test steps, and procedures from OEM manuals.

Technician verified

Scenarios reviewed against the source document — never invented.

Always up to date

New jobs added as brands and codes land in the corpus.