ac wont turn off

[shaun667]

Its a presidential 3 model 7956A856. AC unit and blower runs constantly regardless off tstat setting. We flipped the switch to cool and it never shuts off unless you flip to heat or shut off the main power. Replaced blower relay and sequencer and tested with 2 tstats. Heat side works fine. Even with the tstat wires at the furnace disconnected it still runs. Any help would be appreciated. thanks

[Robert]

Hi,


IF you only have 2 wires connected at t-stat, it is probably a stuck t-stat reversing relay inside the a/c control box.




Thanks,
Robert

[shaun667]

I am not too familiar with furnace setups but the sequencer should be the reversing relay right, and I have already replaced that. I have 26.5 volts going to the ac unit regardless of tstat setting and the ac unit relay is working properly with voltage on without voltage off. But even with the wires disconnect that run to the ac unit disconected the blower still runs. So I am sure the problem is at the furnace, but am really out of ideas.

[Robert]

Sometimes a sequencer is used as the reversing relay.


If all components seem ok, check wires for bare spots allowing them to touch creating a short circuit.



Thanks,
Robert