[clarkgreg]

Hi all,

I'm trying to install a Honeywell Wifi thermostat. The old Honeywell thermostat had the following:

R, W, Y, G (4 wires) plus a Blue wire that was unconnected (presume this to be C wire).

On the furnace end, it's much more complicated:

The wiring board has the following

C (white wire)
G (green wire)
R (red wire)
W (a different white wire)
Y (yellow AND red wire)
TWIN (empty)

The other end of the blue "C" wire is coiled up and pushed away.


So...I think I did something stupid:

I plugged the blue "C" wire into the C slot on the furnace (along with the existing white wire).

On the thermostat end, I plugged in the Blue wire into "C", yellow into Y, green into G and red into R (just like the previous thermostat).

The new thermostat powers up great, so the "C" wire is working! I also have fan control. But the AC unit will not power up


I'm sorry for the horribly complicated message above, but does anyone have any advice?

Kind regards,
Clark

 

[diyorpay]

Guessing your old Th was jumpered from behind R-W (power to heat call) and R-Y (power to cool call) but you could not see it.

C not needed/used. Battery power for Th. G - G for fan.

Jump new Th terminals with small lengths of wire:
R - W Heat
R - Y A/C

Fingers crossed.

 

[BayouRunner]

I don't think you did anything stupid. I think what you did was correct. Now I'm guessing that maybe the thermostat isn't set up properly. I don't have a manual or a wiring diagram or a model of the new thermostat or a picture of the new thermostat wired up, so I can't point you in the right direction. Be glad to help if you can post some more info

 

[supers05]

Sounds like what I'd do.

Make sure that the red and yellow under the Y terminal at the furnace is tight. Also check for the white wire under the C terminal. (the red and white here are in a separate cable running out the the a/c outside.)

At the thermostat, if there are terminals labeled rh and rc or just r, they need to be jumpered together for this setup.

After that, check the thermostat settings. Sometimes they are setup as heating only from the factory.

For extra help, we need the new model number, and possibly a picture of the new thermostat wiring.

Cheers!

 

[clarkgreg]

Thanks for the quick replies...you folks are great!

Here is a photo of the new thermostat. It's a Honeywell RTH9580.

It looks like there is a preset loop connecting RC and R on the new thermostat.

Still having the same problem though

 

[BayouRunner]

Let's isolate the problem. Hook the red and yellow wires together at the thermostat. Turn the power back on. Disregard everything else right now and tell us if the condenser comes on. If it does its a thermostat issue. If it doesn't then something happened to the wiring at the furnace or air handler

 

[clarkgreg]

So I tried the red / yellow combo. It doesn't seem to do anything? Confused

 

[BayouRunner]

In that case it's not your thermostat. Something happened to your wiring going to the condensing unit. Generally one wire goes to the c on the air handler or furnace and one wire goes to y on your air handler which also ties into the y on your thermostat. You'll have to trace it out. Sometimes one of the wires going to the condensing unit also go through a float switch. My best guess is something came apart while you were hooking up the c wire at the air handler. I am assuming that the outside unit has power and that is/was not turned off

 

[clarkgreg]

ok, you were right! something did come loose, now the AC is activating again.

next step please?!

 

[BayouRunner]

I would say wire up the thermostat like you originally did and it should work

 

[clarkgreg]

But that's where I'm stuck.

The fan comes on but the AC doesn't...

Ugg.

 

[BayouRunner]

But that's where I'm stuck. The fan comes on but the AC doesn't... Ugg.

so now you touch the red and yellow together at the stat and the unit outside comes on? If it does and it doesn't work with the thermostat I would say there is some type of set up issue. The manual should explain. Keep in mind also that the thermostat has a five or so minute delay before the compressor will come on when you first apply. Power to the stat

 

[DTRiemer]

I'm no expert but I also think that you did nothing wrong basing on the photos you have shared so maybe how the thermostat was installed is the real issue. I advise that you contact a professional to have it checked if the problem persists.