Turning on "fan only" calls for heat

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Old 07-28-16, 09:44 AM
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Turning on "fan only" calls for heat

Hi. I have a Bryant air handler unit (FB4ANB048000AFAA, not sure how old) and a 4-wire thermostat (Y G W R). A few days ago I removed my digital thermostat to touch up the wall around it, and after restarting the thermostat, the AC stopped working. In order to take the thermostat out of the equation, I removed it and manually tried various permutations of different wire connections. Here are the symptoms:

1) turning on fan (G touches R) turns on fan and calls for heat
2) turning on condenser (Y touches R) turns on condenser but does not turn on fan
3) activating AC (Y G R all touching) -> fan on, condenser off, calls for heat

I believe the prob is with the air handler control board (replacement: HK61EA002) and plan to replace it. Is this a reasonable first course of action? Or could the problem lie elsewhere?

Thanks,

John

PS: why does this control board look so different from other control boards with nicely delineated YGWCR terminals?
 
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Old 07-28-16, 12:08 PM
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Hold off changing the board. Most likely the stat is wired wrong. Are you sure that board is the right replacement?
 
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Old 07-28-16, 02:09 PM
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Hi Skaggsje, thanks for the note.

The bad news is I already ordered the part to be shipped next day air. The good news is, a kind gentleman on another forum suggested the G and W wires might be shorted behind the wall, which happened to be the correct diagnosis: multimeter continuity test confirmed not only short between G and W but also G/W and metal screw that caused the splice and short.

Now I just need to decide how to resolve the spliced wires behind the wall, but at least I'm getting cold air on a HOT day like today!

Thanks,

John
 
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Old 07-29-16, 05:11 AM
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Can you see where the old wires go up through the floor from the basement?either see if there is a little slack or consider fishing a new cable up.
 
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