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-   -   Carrier furnace short cycling (http://www.houserepairtalk.com/f8/carrier-furnace-short-cycling-15871/)

Murph42 04-18-2013 05:56 AM

Carrier furnace short cycling
 
I have a carrier 58GS125-2 furnace. The igniter and the burners light just fine. The main burners stay on for over 4 minutes, then when the blower fan kicks on the burners shut down. The motor does sound a bit more noisy than it should. Do I have a bad motor drawing too many amps? What is my next step? I was told by an expert I most likely have a bad electronic board.

Thank you

kok328 04-18-2013 02:47 PM

If he's an expert then it must be a bad board ;)
However, only thorough diagnostic troubleshooting will reveal the actual problem. I've seen too many people throw money at a unit by replacing parts on a guess and still not get the problem solved. On top of the cost of parts they later had to pay a technician to troubleshoot & repair the unit when all else failed, thus just adding to the overall cost of the problem.
If you are able to check a few things on your own, you might just find the problem.
Can you do an amp draw reading on the blower motor and compare that with the specs on the motor's nameplate?
Are limit switches opening during the cycle and shutting down the unit?
How long after the unit shuts down does it take to fire back up?
Is there a thermostat controlling the fan cycle that is not kicking in soon enough?
What happens when you turn the T-stat to "Fan On" and have the T-stat call for heat?

Murph42 04-19-2013 11:27 AM

When the burner shuts down the blower runs for maybe a minute or less then shuts down, then the igniter starts clicking quite soon after and it starts all over again. I did set the thermostat to fan-on and to heat. The flame did come on like normal and stayed on. I did not check the amp draw on the motor yet. I do know about the limit switch, I pulled what looked like a limit switch and it looked good.

keepinitcool 04-19-2013 05:25 PM

4 minutes is way too long between when the burners ignite and when the blower motor comes on. Sounds like its shutting down on high limit, cooling down when the blower comes on, closing the limit switch, and then going through the ignition process again. You either have a capacitor on the motor that is weak, a blower motor beginning to lock up, or a faulty board. Good Luck!

Murph42 04-21-2013 07:21 AM

I finally repaired my furnace. I replaced the electronic control board and that did the job. Now it cycles properly.

Thank you for the advice.

Bill


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