HVAC Questions? Ask an HVAC Expert for Answers ASAP
Just installed a new thermostat and now the heat won't turn on.
Bill P. :
I am having issues with a honeywell thermostat I just bought and installed
What type of furnace do you have? With a/c or heat pump?
I don't know the brand, it is a gas heater
How many wires were there to put on the new thermostat?
I'm wondering if you maybe blew a small fuse in the furnace?
Is it a normal furnace?
There are 5 wires and I'm going to go up and look at the furnace now
Ok, when you do, find the main power switch to the furnace and shut it off. Then find where the thermostat wire goes into the furnace, it will connect to a computer board of some sort, on that board there will probably be a blade type fuse, 5 or 3 amp
Looks like a automotive type
That is a link to a picture of the fuse
Comfortmaker is the type. It is in the attic
Found the computer board...now what?
Ok, try and have a look for the fuse
I put a link there above. That is likely what you are looking for
Is the fuse going to be behind the panel with all the wires?
Found it..now what?
There's a number "5" on the fuse and and it's plugged into a terminal labeled F1 if that means anything
Yes, that would be the one
Remove it (power is off right?) and have a look
If it is blown, the little metal strip that connects the 2 sides will be broken
Yes, power is off, and the two little pieces of metal in the middle that are shaped like a "z" are not connected. Is that what we are looking for?
Yes, that is right. The z should be solid from one end to the other
Oh, good to know. So, does that mean we just have to replace this and we should be good to go? and where would we find this piece? Home depot? or radio shack?
More than likely yes, the fuse is there to protect the rest of the circuitry. So it will likely be fine with a new fuse
Either one, but I would try radio shack first. Automotive supply store also would be a good place to try
Once we get the new part, should we reinstall the new thermostat? or just put the power back on?
Sure, if that was your plan in the beginning; but if you ever have to mess with the thermostat wires again, or any wires for that matter, just turn off the furnace power first. That way the fuse will not blow
I would leave the old thermostat on for now, put the new fuse in and make sure everything works. Then shut power off and put the new thermostat on, power on and you should be good (the new thermostat may need to be programmed to your preference)
Great! thanks for your help. So, basically we just blew a fuse and that is why it won't work?
Appreciate the help
That is the low voltage circuitry fuse, so since the power was still on when you were changing the thermostat, the wires touched each other and caused a short, so the fuse just pops
You are welcome. If for some reason that doesn't get you going you can come and carry on the conversation later
Well, thanks again!
Replaced the fuse, and it still won't work
Are you using the old thermostat?
We tried, but can't get the wires to connect where they are supposed to.
Does anything work, like the fan on button?
Nope, tried that. We switch heat on, nothing
Put fan on, nothing. Even tried a/c...nothing
There are 5 wires right?
Before we get too far, maybe check the fuse again
Upstairs connected to the furnace, it is a
red to r
white to w
yellow and another red going to y
green going to g
another white and copper going to c
Yet by the panel we have 5 wires
And the fuse is still good
2 of those wires will be going to the outside a/c unit
What do we have for wires at the thermostat?
Do you have the door back on the furnace while you were trying it? (there is a door cutoff switch on the furnace)
A "c" wire that the instructions on the new thermostat say not to use; blue, yellow, green, red, and copper. Old thermostat had copper plugged into "c" and blue was tucked into wall
No we didn't. We will try that now
Should we plug in the blue wire even though it wasn't plugged in before?
No leave the blue unhooked
And leave the copper unhooked from "c" for now too
We don't have a "c" on the new thermostat
That makes that easy then
Do you have a white wire for W by the thermostat? I imagine you do, you just didn't list it
Ok, so with the door on the furnace what is happening and the power on
Putting the door back on now
Then going to flip the power
Woohooo! it's on!
Are we ever going to have to plug in the blue? or are we good for heat and a/c?
No, you won't need the blue. Its not hooked up at the other end
Yep, with the 4 wires you should be good
The "c" wire is for 24 volt power for the thermostat (instead of running on batteries) but I guess your thermostat just doesn't bother with it
Thanks a bunch!
You are welcome!
Have a good night!