I bought a new home in the spring and heating and cooling were working fine with the Trane unit that came with the home. At some point this summer I decided to replace the thermostat as the unit seemed to be coming on too often with the old one. The AC has been working fine since the replacement, but now that its getting colder, I cannot get the heat to kick on. I assume that I've done something wrong when wiring the new thermostat, but I can't quite figure out where I've gone wrong. The wiring on the unit it somewhat of a mess, but I'm pretty sure these are the unit connections coming into the house on the thermostat wire:
W1 & W3 - White
R - Red
B - Blue
G - Green
Y - Yellow

I have a Lux unit thermostat https://www.luxproducts.com/wp-conte..._manual_en.pdf . When I originally wired the new thermostat I remember that it seemed strange how it was wired, but I don't think I have a picture for reference anymore. Anyways, I've tried the following two combinations, but neither has gotten the unit on:
W1 - White
RH & RC - Red
B - Blue
G - Green
Y - Yellow

W1 - Yellow
RH & RC - Red
B - Blue
G - Green
Y - Yellow

This is a natural gas single stage unit with no auxiliary heat. I have pics if needed

Thanks,
Everett

 

I accidentally posted this in the wrong forum. Someone can delete as I re-posted in the correct location

 

You posted it in two incorrect forums. Moved to furnace forums.

You have a gas furnace with a split A/C system.
You have a Trane system which uses the B as common. That means your B (blue) wire should be on the C terminal of your stat. If you have a battery stat.... the blue wire will be taped off and not used.

What I'm concerned with is you said single stage heating but you have two W wires. Two W wires indicates two stages of heating. Check the control board at the furnace. It's down in the blower section. Confirm where those wires are connected.

 

Sorry, for some reason I thought it was a heat pump.

The thermostat does have batteries so I will take the blue off the B.

I've attached a pic of the board, this thing is a wiring nightmare, all the same colored wires and everything running together. As best I can discern, W1 and W3 are the two brown wires running to the top (left) of the board, both those are labeled 'BLOWER'. I believe the two brown wires at the bottom (right) of the board are eventually tied together to the white wire running to the thermostat

 

Yeah.... typical mess of wiring. I don't recognize that board and I don't see any thermostat wiring there.The thermostat wiring would be two brown cables. One to the outside unit and one to the stat. The thermostat cable would have at least a white, green, yellow, red and blue wire coming out of it.

 

I've attached two more pics, one of the thermostat wire and the board where the controls are located on the unit. Its going to be near impossible to see the thermostat wiring, but its as described in the original post

 

I am slightly confused when you say 'two brown cables'. I don't have an indoor air handler, just the outside unit.

 

You have a cable from that location to your thermostat and from that location to your outside A/C condenser.

Is switch #1 on the Lux in the off position.... to the right.... for furnace operation ?
This is your wiring code......

 

Yes, the switch for furnace operation is on. And I have the thermostat wired as the picture you attached. As a last sanity check, I can connect the white wire to red at the thermostat and the heat should kick on, no? If that doesn't work, I assume I'll have to call someone for maintenance.

 

Yes.... you can touch the white wire to the red wire as a test.

 

Okay, so I had someone come out and they replaced the transformer and the unit came on and started working, kind of. It started blowing air out of the exhaust, but it wasn't attempting to pull gas or ignite it. When I first moved in, I noticed it doing this and flipped a switch OFF/ON (I think it was on the gas line) and it fired up and started working fine. It operated for the rest of the spring without issue. Anyways, the technician shorted out a switch and it immediately ignited and started producing heat. They had to order a replacement for that switch and left the wire in as a short. I noticed this morning that the temperature in the house had dropped to where heat should be coming on, but again the unit wasn't doing anything again. The technician came back this afternoon to finish replacing the switch, but now they are saying that the heat exchanger is bad and I need to replace the unit.

Something just sounds fishy here as I don't understand why they got the unit working yesterday with the short over the switch and said everything should be fine after replacing that, even letting the unit run to warm up the house, but today the one thing that pretty much says 'you must replace this unit' is suddenly gone.

 

The switch he shorted out was a safety limit switch. Do you know which one was replaced ?
That furnace does look old based on the pictures.

If it was the flame rollout switch that was replaced then yes.... the heat exchanger is more than likely bad.

Call your gas provider. They have excellent gas techs and charge a minimal amount. Have them check the exchanger.

 

Yes, I found the paperwork and the unit will have been here 15 years in December.

I don't know which switch it was that he shorted, but I will say the unit never fired up at all, so based on the google quick description of that switch, it doesn't sound like the one that was needing a short.

Unfortunately my wife has primarily dealt with them and she doesn't do technical lingo well.

 

That's not terribly old for a gas furnace.

 

Hey PJ, just wanna say thanks for all your help and advice. I'm going to call another company and get another opinion, going to try the utilities company as you suggested.

The guys who came out said they legally must shut off the unit due to the cracked exchanger, but for some reason I wake up this morning and I feel hot air coming out of the vents. Before I could even get outside and see what was going on, the house reached the target temperature and the furnace had shut down.

 

So I talked to the tech to understand how the diagnosis was completed. Its burning 'too rich' so the heat exchanger must be bad....

 

This was a tech from the gas company ?
Usually if they shut down a gas appliance..... it's shut down.

Burning rich so it must be bad is an assumption.... not a diagnosis.

 

No, that's what the guy from the AC company that came out said when I probed further today. I didn't get a chance to call the utilities company yet, but we have CO sensors in the house so I don't feel as rushed