Recently my Carrier 58STA090-16 furnace stopped working. I cannot figure out what is causing the problem.

Here is what I have checked so far with no resolution: :confused: :mad:

• Checked breaker box in garage - no fuses tripped, did a reset anyway

• Checked all GFI outlets throughout house - tested and rest all

• Checked furnace control board fuse - not blown, re-seated

• Installed brand new thermostat with new batteries, heat and A/C still do not work

• Checked furnace control board's status code LED, normally it's solid red, but there is no blinking or anything (dead)

• Checked the electric power meter outside and it is working fine

• There are no other power failures in the house

If anyone has any further suggestions please help if you can.

Thank you very much (in advance)...

Cold in Texas

Check the blower door safety switch. If the door is a bit loose or the switch is bad no voltage will get to the furnace.

You need to check for pimary (120V) and secondary (24 VAC) voltage at the furnace.

If 120 is not present, then the problem is not within the furnace.

If the secondary voltage is missing before and avter the fuse suspect the transformer, otherwise suspect the furnace board.

Typically the 24 VAC is present all the time. 120 VAC does depend on the door switch safety.

Thanks for your suggestions.

How would I go about checking the primary and secondary voltage at the furnace?

You will need a voltage meter capable of measuring 24 volts AC as well as 120 Volts AC. Remove the blower access door and on the back side there will be a wiring diagram for you to follow. Note: If you do not know what you are doing I suggest calling for local ON SITE service.

OK, I think I found the problem. The light switch in the attic had a wire that had come loose behind the cover. Now that I have reconnected that wire and checked voltage, I am good to go. But now I have another question. I removed the transformer to look for damage, etc. but now I cannot remember where to connect the white, black, red, and blue wires back onto the furnace control board. A picture of the transformer can be found here (http://cgi.ebay.com/Carrier-HT01BC11...item5ad5e1695d) and a picture of the furnace control board is here (http://cgi.ebay.com/HK42FZ013-Carrie...219212006r8036). Any help you can provide would be outstanding!

Thank in advance...

There is a wiring diagram on the back side of the blower access door. It is there for specific use of service people who find themselves in your same position. Now you have learned a lesson to always mark the wires you remove so they can be put back.

All units come with a wiring diagram from the factory.

Neutral will be white, L1 will be black

SEC-1 and SEC-2 will be blue and red

Not sure which one is which. Either look at the schematic or if you get a polarity reversed error switch the leads.

OK, I didn't realize the wiring diagram was on the back of the access door (duh), even though I found the same on the internet too. It turns out that the white wire from the junction box was not plugged into the correct spot on the control board. So, I may have fixed the problem too where the 3 AMP fuse on the control board was blowing out all the time (? ). Anyway, I got it all reconnected and the furnace is working now. (Woo hoo!)

Now that I have it all working again, the furnace seems to be louder than normal when running, especially when the blower kicks in. Maybe it's just me?

Thanks for everyone's help. This site is excellent and I will use it again in the future.

DaveW

The federal law requires the wiring diagrams. It is actually put there for safety reasons along with the furnace or unit tag. Glad you got it going.

All, I found the problem. The on-off switch (looks like a light switch) in the attic had a loose wire. This switch is an emergency cut-off switch to the furnace. When I removed the faceplate and looked inside the box, there were small pieces of plastic in the bottom. So after checking further, the plastic had aged and broke loose which cause one of the wires to come off the post. This is why the furnace was not getting any power. I bought a new light switch (o.75 cents) and installed it. The furnace works like a charm. Thanks for all your suggestions and support.

~Warm in Texas!

Glad you got it running again.