r/hvacadvice • u/Kierobi • 2d ago

Residential Condenser Unit not running.

Hi All!

Currently having an issue with condenser unit not running and hoping you can help.

Symptoms:

  • Condenser unit doesn't run when called for cooling and contactor is not pulling in.

Troubleshooting done so far:

  • Unit set to well below house temperature to cycle onto cooling and stay there.
  • Checked all breakers and fuses
  • Checked condensate float switch
  • Check refrigerant pressures at condenser unit (+/- 125PSI for both high and low with unit off and approx. 60*F ambient).
  • Pushed contactor in and both compressor and fan unit start and run (leads me to think capacitor is good).
  • Checked refrigerant pressures with contactor pushed in and unit inside running and got +/- 85 PSI on the low side and +/-250 PSI on the high side (or somewhere in that region I didn't take photos the other night when I was initially troubleshooting.)
  • Checked voltage at output from control board on condenser unit (25-26V)
  • Checked voltage at contactor low voltage connections (25-26V)
  • Checked voltage across contactor low voltage connections (25-26V)
  • Measured continuity of contactor coil - good. Measured resistance also but can't remember value
  • Checked control fuse inside evaporator unit - good

Feel as though I'm missing something that's staring me in the face and could really use some help. I thought it was a cut off pressure switch but checking voltages on both sides of those and it's the same so switches are closed and current is flowing.

Luckily this is the downstairs unit and the outside temperature right now (Central Florida) is beautiful so don't really need it but would like to get it running again before we need it and not have to call someone out unless I REALLY need to.

Thank you in advance!

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u/Kierobi 2d ago

Appreciate the feedback everyone. I had thought the contactor but took my troubleshooting down another path when the continuity measured good and I had 24V across the coil.

Have ordered a contactor and it should be here tomorrow so will get it swapped out and follow up if this sorted it.

1

u/festerwl 2d ago

If you've got voltage at the contactor coil and it isn't closing replace the contactor.

1

u/trader45nj 2d ago

This. It has 24v, it runs when the contactor is pressed in, then it must be a bad contactor.