Trane Split System 2TTR3036A1000A, 2 yrs old

Hi.

The furnace works fine. But when set to cool, neither the air handler or the compressor operate. Also, the "fan only" setting does not run the fan.

I checked the 2 A slow-blow fuse on the board, and it's fine, but I assume that the furnace wouldn't operate if that was blown, anyway.

On the T-stat, I shorted Y to Rc, but no response.

The only thing I can think of is to check continuity between the T-stat and the furnace. Any other ideas?

Thanks.

Check to see if you have 24 volts between c and y at your control board with the t-stat calling for cooling.

If so then check to see if ou have 24 volts outside at the ac unit

Thanks for the help.

There is no voltage at all between Y and C (to clarify for others, this would be AC voltage).

If you have no volts between y and c at the control board then the t-sta must be bad. Take it off the wall and jump between y and r and see if the ac runs

I had previously jumped Y and Rc, according to the t-stat troubleshoot sequence, but nothing happened. I re-read the guide, and it says that for a 4-wire system (like mine), R and Rc should be jumpered. It's not jumpered. So, I jumped them, and the A/C started.

That's strange, because it worked last season. I don't see how a jumper (and screw) for Rc could have gone missing over the winter. I never removed the T-stat, and there's no evidence of a screw or jumper wire. So, I don't know if the jumper was ever there. Anyway, under the assumption that it was, I guess I'll go get a proper fitting screw and put in a jumper.

Correct action?

Yep sounds like you have it figured out. Very odd though indeed