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Discussion Starter · #1 ·
My unit’s blower fan will not shut off automatically and runs non-stop. I believe I have isolated it to something on the Honeywell PCB (47-28827-03) but I don’t know which relay controls the fan. For starters I will explain exactly what I have done to this point and hope this helps someone smarter than me figure out the likely issue. Only way to get the blower fan to turn off was to remove the unit's cover which trips the door's interlock safety swich and kill the whole unit. All 4 tests below had no impact, fan continued to run.
1.Temp mode in either AC or Heat has no effect with fan set in Auto mode.
2.Temp mode turned Off has no effect with fan set in Auto mode.
3.Temp mode turned Off and fan switched to Off.
4.Removed control wires from wall thermostat. No signal going to main unit.
I’m an electronic technician and will have no problem repairing the PCB myself if I only knew what relay I should be looking at. If anyone can point me in the right direction on the relay or provide a full schematic for this board I would greatly appreciate it. It's getting hot here in Georgia and i need to fix this fast and get the wife of my arse. Here are some pics of my unit for reference…
Thank you..
 

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I'm Your Huckleberry
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5,884 Posts
G on the control board is fan. You said in line number 3, "3.Temp mode turned Off and fan switched to Off. ", that the fan stays on continously, even when in "off" so it's not a relay, it's the board.
 

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Discussion Starter · #3 ·
Doc: I was thinking the relay may have locked in the on position. I have seen this in other fields I work in and wondered if it would apply to these styles also? I hate to replace the whole board if it is not needed.
 

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I'm Your Huckleberry
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Doc: I was thinking the relay may have locked in the on position. I have seen this in other fields I work in and wondered if it would apply to these styles also? I hate to replace the whole board if it is not needed.

There is no "on" position, there is normally open and normally closed and yes, contactors have been known to stick but does the relay get power before or after the board?

If you don't have the control wiring diagram than you're going to have to physically trace back the wires from the blower.
 

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I'm Your Huckleberry
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What I mean by that is some times the relay is not on the board but rather it is stand alone but from here I do believe that the little black box or the little white box on the control board is the relay. Some of those boards you can not replace only the relay and some you can. I'd just replace the board and be done with it.
 
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