A/C or Heat doesnt work in "on" or "auto". Fan will not come on at the "on" position either. I changed the batteries in the thermostat. I also read somewhere to disconnect the "Y" and hold it to the "R" on the thermostat for two minutes. That will tell me if the thermostat is the problem. Still nothing worked. I checked to make sure the outlet the furnace was plugged into had power...it does. I then removed the cover from the circuit board on the central air unit. It is a Ducane, it has a Honeywell circuit board. I looked at that wiring for a little while and decided to remove the in coming hot and the "cool" wire leading to the fan. I wired those together and the fan came on. I then (by mistake) put the cool lead back in place but accidently put it on the "continuous on" lead. The fan turned on and wouldn't turn off, can you imagine? After that I cut power and put it back the way it's supposed to be...nothing. Does this mean the circuit board is bad? Or a relay on the board? What is the next step? Replace the board? Or am I completely off base?
thank you for any help you can give.

T-Top

If you have 115 volts in on the transformer and nothing out -bad transformer.

jimbob5

force air furnace wont turn on to heat home. it has been working good but srarted tiday then stopped now wont come on. what can be the problem??? i have an electric heating system

Hartrobinson

I found this other question and answer i copied and posted below. Do I need a fuse before my transformer for any reason, or does that 5 amp fuse handle that? Also, does the replacement need to be identical? Where is the best place to get one? Radio shack?

thanks again for saving me so much money.



BobkatAug 7, 2005, 09:32 PM
my old lennox hvac transformer blew, it was a Basler be11349rcd29, 120volt to 24 volt 50/60 cycle, it has a white and a black wire comeing from it, I want to add a fuse to the correct line, I don't know much about electric stuff, how or where do I find a correct and affordable replacement part, and to where and how do I attach the fuse, or would there be a replacement unit with a fuse box on it, a good usefull part number replacement would also help,
Thanx

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labmanAug 8, 2005, 01:20 AM
Do you have a Radio Shack nearby? If so, go buy a 273-1512 heavy duty transformer, a 270-1281 inline fuse holder, a pack of 270-1005 one amp fuses, and maybe 64-3057 assorted wire connectors. These are out of an old catalog, so I can't promise they haven't changed the part numbers. Also, make sure if the old transformer has a amperage marked on it, it isn't over 2 amps output.

If you don't have a Radio Shack, you may be able to find the stuff at a hardware store or home center. Auto stores may have the fuse holder you need. The part numbers I gave you are for the traditional 1/4'' fuses. You may have to buy 5 mm ones now. Just make sure the fuses and holder match.

Shut the power off to the furnace. The transformer should have 2 black wire on each side, plus a yellow wire one. On the side with only the 2, connect one to the white wire from the furnace. Connect the black wire from the furnace to the fuse holder, and the fuse holder to the other wire on that side. Put in one fuse. Ignore the yellow wire, maybe capping it with a wire nut so it never connects anything. Connect the 2 black wires on that side to the red and blue wires to the furnace controls. You have a new, fuse protected transformer likely all for less than $20.

T-Top

If you have power at the transformer.(115 volts) and nothing on the low voltage side- two wires leaving the transformer to the control board. You have a bad transformer.

Hartrobinson

T-top, what I'm asking is, when I replace the transformer, with a new transformer, should I add an inline fuse for any reason....like the guy was talking about above?

AND does the replacement transformer need to be to the exact same specs? Where do you get something like that?

Hartrobinson

I've gotten a transformer and installed it. Now, the fan will run, but as soon as I turn the thermostat to Cool. The 5 amp fuse blows. Is something with the outside unit causing that? What is the next step?

labman

All right. You have a short in the pair of wires that runs out to the relay for the compressor. A small chance the relay coil is shorted. All the relay needs is a pair of wires running from the Y and com terminals at the furnace out to it. Sometime they run a multi conductor cable and use the yellow and blue wires. Sometimes they run a pair of any colored wires. Trace the cable and repair/replace as needed. You may be able to switch to other good conductors in the cable. I learned the inline fuse trick after chipmunks chewed the insulation off my thermostat wiring in an inaccessible place.

Can't resist this, I have had worse chewing problems since.

labman

Go to the sticky at the top of the forum. Work you way through it, and if you don't find your answer, post back with details. Do you have power, a flashing red light, relays that click, are the breakers all on, etc.?

Hartrobinson

Labman, t-top-letmetellu,

Ya'll were very helpful. Labman, you hit the nail on the head, it was the coil. Turns out, according to the guy I had to get to help me, the coil failed, and had an internal short. The short fried the transformer. All of this happened without blowing the 5 amp fuse initially. Then, with the new transformer, the 5 amp blows. Don't ask me. I'd love to hear anyone's explanation for that. At any rate, thank you all very much. It cost me about $80 including paying the moonlighter $55. I love this site now!

hvacservicetech_07

i would say you have a bad transformer- if you have 120 volts to the transformer and nothing coming out then it's bad.....be sure when purchasing a new one that the voltage and the VA are the same