Removing boiler thermostat wires causes AC not to work.

[Cpeters]

No problem with the ac until I removed my boiler thus 2 wires not connected. I currently have a rite temp
thermostat from HD. Had it for years. I now only have a yellow, green and blue going to the blower and that's it. I disconnected the red and white because it's no longer used. Not putting the boiler in until Aug-Sept. When I sent the temp down the unit (carrier fxd) hums a little but that's about it. I have the yellow hooked up to Y and tried Y2. The Blue to RC and the Green to G. I was thinking the transformer was shot and it was running off my boiler transformer some how. Probably had it wired wrong from the start. Thanks.

 

[Stuff]

Need to check at the air handler (blower) to see what's hooked up. With those colors the wires are likely spliced somewhere in between so you'll need to trace them.

 

[Sponsor]

 

[WorthFlorida]

The red wire is the 24 volts from the furnace or air handler. The 24 volts from the red at that RH must be connected to the RC. There probably is a strap between the two. Google “thermostat wiring”. Could also be you disconnected a common between the two systems, usually the white wire. If two transformers are used there be no strap. Is the blue at the air handler for the ac connected to the transformer?

Y2 is for two stage cooling systems. At the thermostat you need 24v at the RC and the thermostat switches it to the Y for cooling. With a wire you can jump the two to turn on the AC.

If your thermostat uses batteries, it’s for the display only, programming if any, and to operate the thermostat. With all wires disconnected you’ll still see a display.

 

[Cpeters]

The red wire is the 24 volts from the furnace or air handler. The 24 volts from the red at that RH must be connected to the RC. There probably is a strap between the two. Google “thermostat wiring”. Could also be you disconnected a common between the two systems, usually the white wire. If two transformers are used there be no strap. Is the blue at the air handler for the ac connected to the transformer?

Y2 is for two stage cooling systems. At the thermostat you need 24v at the RC and the thermostat switches it to the Y for cooling. With a wire you can jump the two to turn on the AC.

If your thermostat uses batteries, it’s for the display only, programming if any, and to operate the thermostat. With all wires disconnected you’ll still see a display.

Everything worked fine with the boiler attached. I'm wondering if it was running off of the boiler transformer. When I shut off the boiler emergency switch the ac wouldn't work so I left it on all the time. I only use the blue for RC, the green for the fan and yellow. I jumped the rh and rc and the
y and y2 and nothing changed. I'm tending to think the transformer may be shot. I do hear a humming noise when I turn on the emergency switch.
Im thinking the transformer may be the problem and may have been the problem all along.

 

[Cpeters]

Everything worked fine with the boiler attached. I'm wondering if it was running off of the boiler transformer. When I shut off the boiler emergency switch the ac wouldn't work so I left it on all the time. I only use the blue for RC, the green for the fan and yellow. I jumped the rh and rc and the
y and y2 and nothing changed. I'm tending to think the transformer may be shot. I do hear a humming noise when I turn on the emergency switch.
Im thinking the transformer may be the problem and may have been the problem all along.

Thanks for the help.

 

[WorthFlorida]

If you're running two independent systems from one thermostat, two 24v transformers from each unit is a better way, however, because of not enough wires just one transformer gets used. Since your going with a new furnace, if possible, run new thermostat wires. New HE furnaces, heat pumps/AC are sometimes two stage so more wires are needed. If you replace the thermostat with WiFi , (highly recommend) you'll will need a C wire (common).

LOL

 

[Cpeters]

Thanks for all you help, today I'll run for a new thermostat and a voltage tester. Then I can tell if Im getting 24 volts from the transformer, if not,
I'll replace.

 

[Cpeters]

Problem solved. 3 amp fuse blown. tested the transformer and it was 24 volts and ok.
I put the boiler in after hurricane sandy so the fuse must have blown around then. Could
never shut the emergency switch on boiler otherwise the AC wouldn't work. Since I removed
the boiler the transformer was disconnected.

 

[WorthFlorida]

Thanks for the update.