Twice this week, ‘dead’ air handlers were just a tripped float from a clogged condensate tee. Kill power, vacuum the tee with a shop vac, ohm the float, and confirm 24V at R to C — 5 minutes and you’re done; anyone else make this their first check?
After I ‘vacuum the tee with a shop vac,’ I hit the trap from the air handler side with a little hand pump and then pour a cup of water to prove flow and watch the float drop before chasing 24V at R–C. Small caveat: cap or tape the vent on the tee so the vac pulls crud instead of air. You carry a mini pump on the truck or just rely on the vac?