Intermittent Blower Fan


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Old 05-10-13, 10:01 AM
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Intermittent Blower Fan

I tried to search for a problem like mine, but didn't find anything. I replaced my t-stat about a year ago, & had no issues with heat or AC. When the temps were warm enough to use AC this year, the blower fan was intermittent. A commercial HVAC guy (family friend) looked at it, verified coolant & put a meter on several connections near the fan & couldn't find a problem (it chose to work while he was here). He recommended changing the t-stat again, which I did (2 different models of Honeywell units), but the problem is still there. It may take days or a week to stop again, but it does eventually. When it happens, I can't turn the fan on manually either. I can switch to heat & the fan will work fine. After playing with it or letting it sit, I can get the fan to work again in AC. Of course, the lines freeze when it stops. At this time, I have no other issues than the fan. Any ideas?
 
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Old 05-10-13, 11:17 AM
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I'd think either the control board or the blower motor itself. The A/C and heat use different fan speeds, thus different current/voltage paths and different relays in the control board. A weak relay that overheats and doesn't hold under load would explain it. You'd need to check for voltage AT the motor when it stops. If no voltage, then likely the control board. If it has voltage but the motor isn't turning, feel the motor to see if it's very warm.
 
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Old 05-10-13, 03:51 PM
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Thanks, I'll check. On a side note, the fan will run sometimes even if I remove the t-stat. I wouldn't think this is correct, but it does it.
 
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Old 05-10-13, 04:04 PM
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If you unwire the thermostat from the wall and the blower fan is still running .... then it sounds like a control board issue.

A make and model of the furnace would probably be helpful.
 
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Old 05-10-13, 04:10 PM
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Ahh...new info....yep...sounds like a control board issue. That's if it does it in A/C only. In heat it might keep running for a while to cool down the heat exchanger...even with the stat disconnected...I think.
 
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Old 05-10-13, 04:15 PM
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It does it in AC.


Goodman heat pump

Outside unit: CPKJ42-1
Inside unit: AR42-1
 
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Old 05-11-13, 12:23 PM
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Where is the best place to find a control board? An internet search brought up several different kinds & none of them seemed to be "the one" for my application. I'm looking for a direct replacement.
 
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Old 05-11-13, 01:54 PM
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It is either a B1370735 or B1370738

http://johnstonesupply9.com/TechDocs...t%20RP-265.pdf
 
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Old 05-11-13, 02:44 PM
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That was a big help. Looks like I can get a new one plus a new relay (assuming you guys recommend replacing it with the board) for $50 or so. Any tips on replacing it? It seems like it would be straight forward, but I don't want to fry anything, especially me.
 
 

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