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mbsmith81
New thermostat wiring

Hello everyone,
I replaced the older Sears HVAC thermostat the other evening. It's wired up as a 4-wire, with a jumper between Rc and Rh. The sheath containing the 'stat wires is labeled "Type 5", so I'm assuming it used to be a 5-wire; I've found a 5th blue wire that someone cut off, and it's not connected to anything in the old thermostat.

I installed a new Honeywell programmable model, and wired it up with the wires going to the same terminals. I turned the A/C on, and the blower unit and the compressor outside kicked on. It ran for a few minutes, then stopped, but the icon on the 'stat showed that the AC was still running. I checked, and the compressor outside was still running, the blower motor had stopped though.

I turned it back off, waited, turned it back on, same thing; blower not coming on. I turned it back off, and turned the fan from Auto to On, and the blower didn't kick on then, either. I tried re-seating the wires in the terminals to make sure they had good contact, but nothing changed. I'm pretty sure this is a good thermostat, I used it in my apartment for over a year, and took it with me to the house (not to mention that it worked for a few minutes before the blower motor shut off and wouldn't come back on).

I've re-installed the old Sears 'stat, and everything works correctly again. Anyone have any ideas of things I can check/try before purchasing a new thermostat?

Sten
Re: New thermostat wiring

You should always make sure that the wire is going where it's supposed to, there's been times when the wires don't make sense and have to be traced out, I remember working on a rooftop with all red wires. Did you put new batteries in the stat?? Believe it or not some stats have a dip switch in them that wants to know what type of fuel is being used for heat, I believe this should be in the correct pos. for the stat to work right in the cooling mode as well as heat but could be wrong

Here you go so long as the connections are correct at the furnace and condenser;
- Black should be the common wire "C" terminal
- White is the heating wire "W" terminal
- Green is the wire for the fan control "G" terminal
- Yellow is the cooling circuit "Y" terminal
- Red is the 24v power; you have an Rh (heating) and an Rc (cooling). Connect the red to either Rc or Rh and wire a jumper between the Rc and the Rh
- Blue is used for second stage cooling

mbsmith81
Re: New thermostat wiring

Yep, I put a fresh set of batteries in the thermostat beforehand, and I made sure to set the jumper on the back to HG (gas furnace) and not HE (electric furnace). I didn't even try running the furnace to be honest.

I drew a crude schematic beforehand of where each wire went in the old thermostat before disassembly. This one is pretty simple, all four wires are different colors, and each color corresponded to the matching terminal in the old thermostat (G to green, Y to yellow, etc).

I've been searching the internet, and I'm still unable to find any troubleshooting info as to why the blower would stop working, and running it manually wouldn't work.

Sten
Re: New thermostat wiring

It has to be the stat if the old one works fine, and the wiring is OK. I'd go to Home Depot or Lowes and get a new one, if it works then your good to go, if it doesn't then bring it back. You've got nothing to lose, I've gotten new parts at HVAC Supply Houses and they've been bad, very rare but it happens. Good Luck!!! :)

mbsmith81
Re: New thermostat wiring

That's what I was thinking could be the culprit, but I'm trying to rule out any other problems before dropping some more cash :D

I was looking up part #s for better detail to the problem, and it appears the digital model of Honeywell stat I have is pretty much the cheapest one they make, and doesn't seem to rate all that well. Just seems odd that it decided to die during the move. Oh well, thanks for the help!

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