[Ondverg]

I have a Carrier heating/air conditioner unit. A few days ago it stop working. It constantly blows cold air. We turned the breaker off a couple of times hoping to reset it, but this didn't work. I put in a clean filter and that didn't work either. My son checked it and said that he think it is the circuit board (he's not trained electrically, but is very intelligent when it comes to breaking down computers and putting them back together). I would like an opinion as to whether replacing the circuit board is the solution or if this is a symptom of other problems with my unit as well. Do I need to submit more specific details? I can't think of anything else to add at the moment, but please tell me if I need to give more details about what I see or what is happening with the unit.

Thanks

[KC13]

Model #s would go a long way toward identifying what you have there.

[Ondverg]

I'm sorry. The model # is 58gp075-pa.

[KC13]

You mentioned changing the filter - was it clogged? The blower runs continuously? Check the main limit control. It may be stuck open. Try tapping the middle of the fiber plate with the butt of a screwdriver. Look for other limit devices that may have tripped open.

[Ondverg]

No, the filter was not clogged, I just changed it based on the advise of someone who suggested that I try it to see if it would be an easy fix. Unfortunately, it wasn't that easy of a fix. The blower does run continuously. I will show the information you sent to my son asap and have him check everything you suggested.

Thanks

[Ondverg]

Please disregard this post. It's an edit due to hitting 'send' twice accidentally.

[Ondverg]

I still have not resolved this problem. I have been using electric heaters and a fireplace, but the temperature is about to decrease so I would like to make sure this is an easy fix before calling a repair service within the next day or two. I have attached a pic of my furnace. Will you please let me know if you can see the "main limit control" in my photo and point out anything else I could possibly check?

Thank you

[KC13]

The primary limit control does not appear in your pic - it is mounted in the main cell panel, just behind the gas control, with 2 wires connected. For test purposes, you could try removing the wires & connecting them together. THIS IS ONLY A TEST. Do not leave unit in this condition as a remedy. If heating operation is observed, the limit has been "tortured" by overheating, and the cause must be determined & corrected.

[Ondverg]

I have attached a couple pics of the main cell panel. Will you please point out the wires so that I can be sure I'm looking at the correct ones? I may still have to call someone with experience to come check it for me, but at least I will be able to articulate what I need them to check first.

Thanks

[KC13]

From your latest pics, I'm seeing tell-tale signs of a potentially serious problem. The black upright rectangular device behind the gas control is the primary limit switch. On the right-side terminal is the fusible link, which looks to have had the lead wire re-attached with a wire nut. The spark relighter housing looks somewhat melted, the primary limit device shows some discoloration that gives the appearance of exposure to flue gases, and the center cell looks questionable. I would advise you at this point to call in a pro, and have the unit inspected for possible heat exchanger failure.

[Ondverg]

Kc13, thank you so much for all your help. This really means a lot to me. I feel much better now about calling a professional. "Askmehelpdesk" is a godsend! Have a wonderful 2010! :-)

[hvac1000]

KC13 I concur with your recommendations. GREAT CATCH KC13. You should be very busy right now in our neck of the woods. Been fielding phone calls from some of my students from a few years ago who are now out in the real world trying to fix equipment. The fun cold weather brings especially on roof top units..

[KC13]

Gosh, thanks guys... I'm... speechless... don't worry, I recover quickly. :p