50A51-495 2-flash led indication; direct blower on/off/on/off

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Old 09-02-11, 09:13 AM
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50A51-495 2-flash led indication; direct blower on/off/on/off

Model UD/DD-R FURNACE: Got a plugged drain line, and the pan inside filled and overflowed down into the furnace area. No water on 50A51 White-Rodgers CNT-2184 control board, which is good. But I have a 2-flash led indication on the board(cool mode), and my direct blower is on/off/on/off at 1 to 2 second intervals. I unplugged the drain line, which then drained the pan. Wiped up water (very little) on bottom of inside furnace (all is dry). But still have this flashing and on/off blower problem. No water inside the bottom of squirrel cage now. There has to be very little, if any was inside there. How do I rectify the flashing problem? Thanks for all the help and suggestions.
New observation: I have changed over to heat from cooling, on the thermostat, and see a continuous flashing on furnace control board, and the burners light up. Blower is constant speed blowing (no on/off/on/off) with heat. So placed back to cool mode, and flashing (initial flash/.25 second flash/.75 second flash) with relay switching on/off power to blower (hear the clicking). Could this be a normal direct blower operation?
 

Last edited by boowoo; 09-02-11 at 10:17 AM.
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Old 09-02-11, 04:41 PM
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Sounds like a blower relay problem in the furnace control. Here's a link to a furnace manual including a section on the control. I found nothing in there similar to what you are experiencing but I could have missed it in a quick look. http://hvac.amickracing.com/Furnace%...ion%20(99).pdf
 
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Old 09-02-11, 06:16 PM
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Thanks Grady

Thanks Grady for finding this site with a flow chart and troubleshooting guide. Helped out a lot. I saved it so as if I ever need other technical info on my system, it will be handy. I just wish I had a schematic to the CNT 2184 (50A51-495 ) board. There are a number of relays on the board itself. I guess I will trace the foil runs from the pins on the relays to the output pins for the blower. One of them has to be it. My only question would be why the motor was shutting off, then coming on quickly, then shutting off (cycling). Sounds like a capacitor problem of ramping voltage or a zener gone bad. I hear the relays on the board clicking in operation.
 
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Old 09-03-11, 06:09 PM
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The clicking is what makes me think the problem is in the board. If it were a motor cap, the relay would stay pulled in. Just as a test, try turning the thermostat off & set the stat's fan switch to "on". My guess is you will experience the same thing.
 
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Old 09-07-11, 11:44 AM
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Originally Posted by Grady View Post
The clicking is what makes me think the problem is in the board. If it were a motor cap, the relay would stay pulled in. Just as a test, try turning the thermostat off & set the stat's fan switch to "on". My guess is you will experience the same thing.
After a day of running (on/off/on/off) it started to run normal, and the blinking led indicator ran normal operation (1 sec on/1 second off). Must had been humidity affecting the board and it dried out. No problems since. Thanks again Grady.
 
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