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joezimm · May 20, 2007, 02:36 PM

Here's my issue.

I cannot turn on either my AC, Furnace, or Blower from the thermostat. However, I can turn on the blower by manually pressing a 'Manual On' button inside the furnace.

- AC is powered and was working a couple days ago.
- Furnace was also working a couple days ago.
- Found furnace breaker tripped this morning when I noticed the problem. Turned both Furnace and AC breaker Off, then On again.
- Installed new Thermostat, but problem persists.

That's about it. Anyone have any suggestions?:o

Thanks in advance for any help.

hvacservicetech_07 · May 20, 2007, 02:39 PM

Is there a low voltage fuse in the furnace, near or on the transformer or circuit board that might be blown?

joezimm · May 20, 2007, 02:41 PM

Let me check...

joezimm · May 20, 2007, 02:51 PM

Not sure. What does it look like? I don't see anything that looks like a fuse.

It's a York Stellar furnace by the way.

hvacservicetech_07 · May 20, 2007, 02:58 PM

Does it have a circuit board?

hvacservicetech_07 · May 20, 2007, 03:00 PM

First, Make sure you have voltage to the furnace, find the transformer and test the primary and secondary sides of the transformer, you should have 120 volts on the primary and 24 volts at the secondary. If the furnace has a circuit board it should have a little fuse that looks like a "car fuse" plugged in somewhere on the board, usually near where the 24 volt comes in.

joezimm · May 20, 2007, 03:04 PM

I don't have a Volt meter, but I can turn on the blower manually inside the furnace by pressing the 'Push Manual/Pull Auto' button.

There is another section on the top portion of the furnace that I assume is the circuit board which is in a plastic enclosure. It has a red LED light that is not on or blinking.

hvacservicetech_07 · May 20, 2007, 03:05 PM

It sounds like you have lost low voltage, Did this problem start before you installed the new thermostat?

joezimm · May 20, 2007, 03:06 PM

Yes. I noticed the problem yesterday evening and noticed the tripped circuit breaker this morning. I replaced the Thermostat this afternoon.

hvacservicetech_07 · May 20, 2007, 03:06 PM

The button you are pushing is probably just the combanation fan/limit switch. This means at least you do have power to the furnace.

hvacservicetech_07 · May 20, 2007, 03:07 PM

Has the breaker tripped anymore?

joezimm · May 20, 2007, 03:07 PM

So, can the blower turn on manually even if there is no low voltage?

I'm trying to track down my owner's manual to see if there is a low voltage fuse or not.

And no, the breaker has not tripped again.

hvacservicetech_07 · May 20, 2007, 03:10 PM

Yes it can. Without seeing it, I'm guessing you have a shorted transformer. Can you find the schematic for the furnace?

joezimm · May 20, 2007, 03:29 PM

Found one on the inside panel.

hvacservicetech_07 · May 20, 2007, 03:47 PM

Is it showing a fuse in the circuit?

joezimm · May 20, 2007, 03:50 PM

Is it marked 'fuse' or is it some special symbol?

joezimm · May 20, 2007, 03:54 PM

Yes, it says [FUSE] on the Elementary diagram between a BLK<3<--BLK and a -O DS O- Power Supply. So is that near the transformer? I don't see any other fuses.

hvacservicetech_07 · May 20, 2007, 03:57 PM

Can you find this fuse on the furnace?

hvacservicetech_07 · May 20, 2007, 04:00 PM

You really need a voltage meter, so that I can run you through some simple check points.

joezimm · May 20, 2007, 04:18 PM

Still can't locate a fuse. Not sure what else I can do at this point.

If you have any other ideas, just lmk. Otherwise, thanks for all your help.

-j