They Attempted the Repair Themselves First (Decision Tree)

Why this matters

The customer tells you up front: they watched a video, took a swing at it, and it did not go well. This is different from finding old undisclosed work inside a unit. It is fresh, it is disclosed, and the system was disturbed within the last hours or days. That means two things at once: it may have been left in an unsafe state, and you now have two possible faults tangled together, the original problem and whatever the attempt introduced. This tree keeps you safe first and keeps those two faults from getting confused.

Start here: stabilize the fresh disturbance before you diagnose

A just-attempted repair can be left mid-step and unsafe. Before you diagnose anything, verify the system is in a safe state, do not assume it is:

• Do not energize or pressurize on the assumption it was left correct. Verify it is dead or isolated first.
• Check for a live conductor left capped, exposed, or reconnected wrong, a missing ground, reversed polarity.
• Check for gas left on, a fitting not leak-checked, an appliance left unpurged.
• Check for water left under pressure, a valve left open, a sealed system opened.
• Check for a defeated or unreset safety they may have bypassed to test their fix.

If anything is in an unsafe state, make it safe before you go further: de-energize and verify dead, shut off and relieve pressure, close and lock the supply. A fresh attempt is the most likely time to find a hazard someone stopped in the middle of. Stabilize, then diagnose.

Step 1: get the full account of what they did

Their attempt is data, so collect it without judgment. Ask for the whole sequence:

• What did you try, in what order? Parts swapped, wires moved, settings changed, things disconnected.
• What did you put in, and where did it come from? A wrong or miswired part changes what you are looking at.
• Did anything change after you tried? "Worse after" is the key phrase. It tells you the attempt created a second issue on top of the first.

Write it down. You are building the list of everything that has been disturbed, which is exactly what you need for the next step.

Step 2: separate the original fault from what the attempt introduced

This is the whole point of the tree. You are now looking at a system with potentially two faults, and treating them as one is how you misdiagnose:

• The original fault is what they were trying to fix. It is probably still there.
• The introduced fault is anything the attempt broke, reversed, half-installed, or left disturbed.

Work out which symptom belongs to which. A reversed connection, a tripped safety, a half-seated part, air or contamination in a sealed system, a stripped or cross-threaded fitting: these are attempt-introduced and can mask or mimic the original problem. See related: Diagnosing a System After a Failed DIY Attempt, for the method of isolating the two.

Step 3: decide how to proceed

• Diagnose as-found when the attempt is clearly reversible and has not muddied the picture: you can see exactly what they changed and undo it in your head. Confirm the original fault directly.
• Reset to a known baseline first when the attempt disturbed too much to trust the current state. Undo their changes back to a clean starting point, restore any defeated safety, reseat what they moved, then diagnose from there. You cannot read a system you cannot trust.
• Stop and disclaim when you cannot make it safe today, or the attempt caused damage that changes the scope beyond what you can responsibly do on this visit. Lock it out, document the as-found state with photos, and quote the real scope, which now includes undoing their attempt.

Quote what the attempt actually changed

The final scope often includes undoing the DIY layer, not just the original repair. Be clear: "There is the problem you called about, plus we have to put right what the attempt disturbed." Separate the two on the quote so they see the difference between the fault they had and the work their attempt added.

The recap

1. Stabilize any unsafe state before diagnosing: verify dead or isolated, relieve pressure, restore defeated safeties.
2. Get the full account of what they did, in order, without judgment.
3. Separate the original fault from anything the attempt introduced; treat them as two problems until proven one.
4. Decide: diagnose as-found (clearly reversible), reset to a clean baseline first (state untrustworthy), or stop and disclaim (unsafe or out of scope).
5. Quote the real work, including undoing the attempt, and split it from the original repair.

References

• OSHA guidance on hazard recognition and lockout/tagout; NFPA 70 and NFPA 54 on electrical and fuel-gas safety
• Trade-standard practice for as-found documentation and prior-work scoping
• See related: Diagnosing a System After a Failed DIY Attempt; The DIY Repair That Created the Fault (Decision Tree)