Said It Here

Thermostat doesn't work after opening it up

Opening a thermostat can cause wiring disconnections or blown low-voltage fuses, which leaves the HVAC system unresponsive and prevents the control board LED from lighting up. These issues typically stem from loose wire connections or accidental shorts made during inspection, stopping the heating and cooling from responding to thermostat commands.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

  1. 1
    Checking fuses and access panel buttons
  2. 2
    Manually tying the R, G, and Y wires together
  3. 3
    Trying another new thermostat

In their words

Unedited, most upvoted first, each linked to the thread it came from.

“I can't figure out why the fan won't shut off at all, even with the system off it keeps running, and when I switch to cool, the heater starts blowing.”source ↗

WadeWickson · r/hvacadvice · 2 upvotes

“Currently I can control thermostat but HVAC doesn’t respond. The LED on the control board PCB doesn’t glow either. I checked the fuse is not blown and checked with access panel button pressed.”source ↗

supercharger6 · r/hvacadvice · 1 upvotes

“Put on a new thermostat. Compressor wasn't coming on, condensor fan was tho.”source ↗

“Took the thermostat off and tied the R G and Y wires together everything turns on and runs fine.”source ↗

“When I put the thermostat back on then the compressor won't kick in. I'm stumped. Any idleas? Tried another new thermostat and same result”source ↗

badinformationterry · r/hvacadvice · 1 upvotes

Where this came up

r/hvacadviceapplianceshvacthermostattroubleshootingwiring

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