My thermostat wires aren't getting any power. I tested the red and blue wires for AC voltage on another thermostat in my home and it returned 27 volts, but the one in the photo here had no voltage. I reset all the circuit breakers and nothing.
Where to start.... yes.... at the other end.
What is at the other end ?
Gas furnace with A/C ?
Possible blown fuse on furnace board.
Possible tripped condensate float.
That would be controlling the gas furnace and one split A/C with one condenser.
The other two condensers would have their own air handlers and thermostats.
So your problem is going to be at the gas furnace. There will be an R and a C on the furnace board.
Check for power there. If it's not there you'll need to check further. Defective/bad transformer would be next. Open high limit switch will also shut down R/24v power.
Remember.... when the blower door is open....main AC power is disconnected from the furnace and it will be dead. Since the control board is in the blower section you'll need to hold or tape the safety switch in.
Without more info on your furnace I can't offer any more detailed help.
Pictures are a BIG help..... How to insert pictures.
1. The fuse tested positive for continuity, so I reinstalled it.
2. Removing the panel turned off both the upstairs and downstairs thermostats. The guest room still stayed on. You can see the photos of the control board.
3. I noticed that one cable had only white and red circuits while the other had all the colors connected to the control board. The white circuit in this one appeared to have loosened from the W terminal. I reattached it but still no power to the downstairs thermostat.
4. Only one red cable gave off any voltage. The other had none.
The separate white and red wires go to the outside condenser.
The five wires go to one thermostat. There should NOT be two thermostats connected to one furnace. Do you have a zoning system ?
Little confused.... you moved the white condenser wire to W in first picture and then moved back to C in the second picture.
Is the red fault LED flashing ?
I've labeled one of your pics. You need to confirm you have 120v to the board. Check from ground to both side of the safety switch with switch in. Check L1 on main board. If yes.... check for 120v from L1 to L2. If ok.... check for 24vAC coming out of the transformer.
Sorry that one's the wrong furnace if that's the case. I went to the furnace next to it - a smaller unit - and opened up the panel it doesn't appear to be getting electricity. Let me see if I can double check the circuit breaks and such first.
here's a photo of the circuit board. Should that blue cable be loose like that?
I pulled the transformer. See attached. Do I have to get the same model or the same spec? I'm guessing if if it'll screw into my housing is another important concern.
Wiring.... you mean at the stat ? Yes.... that is ok.
There are many transformers to choose from. The mounting feet location should be universal.
You need 120v in and 24v out. Most are multiple taps. You just choose the wires you need.
Cap the extras. Endurance transformer Control transformer Emerson transformer
So I installed a used transformer today and that did the trick, thanks PJ. But one thing I'm noticing is that there is a humminh noise coming from it that the other transformer in furnace #2 isn't having. Is that a concern?
The humming is not a problem. Make sure the mounting screws are tight.
If the noise is objectionable..... notify the seller of the issue and they should send you another one.
I have a Luxaire gas furnace fires up good runs heats for about 5 minutes flame goes out blows cold air
it has a washable filter and thats clean i cleaned the flame sensor same thing. i bought a new pressure switch off ebay matching number one the one that was in my furnace installed it. furnace worked good for a week i come home today furnace blowing cold air has 8 red flashes . i shut furnace off and started back same any ideas
Hello — I have an Evcon furnace, model number RGF1L080BP12MP11A. I'd like to run the fan on this in the summer, as I've read that doing this to circulate the air in your house can help keep the temperature down. We live in a pretty old house without central air, and anything we can do would be a big help.
I have an Emerson thermostat, model 1F78-144 — a cheapo thing our electric company gave us when a power surge killed our old one. I can set the fan to "auto" or "on," and the system to "heat," "off," or "cool." From what I've read, I need to set the fan to on and the system to cool, then set the temperature below whatever it's currently reading as. Unfortunately, this isn't turning the fan on.
I've removed the panels from the furnace and don't see any kind of switch I could hit to turn on the fan. I've seen that sometimes you need to install a "summer switch" to accomplish this. Is that what I need to do? Or do I have what I need already and just not know what I'm doing? Probably incidental, but I read that you should shut off your gas at the valve, and have done so.
Thanks in advance for any advice you can give. If it's helpful, I can get shots of the furnace with the panels off, or anything else that might be of use.
05-03-22, 04:44 PM
