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NickMN 06-23-2012 12:50 AM

no response from fan, central air or furnace
Hello everyone,

I'm battling an issue with my hvac system. Last week I went to turn on the central air with no response, turned fan from auto to on and again zero response. Furnace with heat turned up and nothing. I checked all breakers and none were tripped. I swapped out the thermo just to check and no response there either. Based on some basic searching online it appeared maybe the fan control board was the culprit, I purchased thru grainger and installed it today with zero difference on the situation.

Bryant 397haw036080 furnace from 1982, paired with a Rheem central air unit.

Any ideas or what I can check next now that I have checked out the board and thermo? The fan moves freely, have never had any issues in the two years I have owned this house. I have a multimeter and did check volts coming in from breaker on old board was was right around 120v.

thanks in advance, I really don't want to call out someone! :thumbsup:


beenthere 06-23-2012 04:49 AM

IS the transformer working. Do you have 24 volts between R and C of the board.

biggles 06-23-2012 06:01 AM

remove the stat and jump R to G on the subbase for the FAN....yes/no? then go down to the board and jump R to G on the board for the FAN..:huh:is anything lit led or stat screen?

NickMN 06-23-2012 02:53 PM

1 Attachment(s)
Thanks for replies!

I have ~29 volts between R and C on the board. Also 120 volts at PR1 and PR2 along with 29 volts at SEC1 AND SEC2 from transformer.

The flashing LED is on new board (old one didn't have it). I'll try the jump wire next.

thanks again fellas

attached is the board swap I made

biggles 06-23-2012 03:15 PM

wonder...did you jumpp R to G on the old one?

NickMN 06-23-2012 03:26 PM

No, I did not make that jump on the old board...

NickMN 06-25-2012 11:51 AM

I should add the prior weekend on a hot sunday when I was gone all weekend I got home and turned on the central air. It kicked on fan included and ran for about ten minutes. Never came back on, I thought it was originally because of the electric saver program I'm on with my utility. Obviously not the case now.

Any other ideas of where to check?

Doc Holliday 06-25-2012 12:26 PM

Check r-c at board and at stat.

at furnace: r-c just shows low control voltage which you said it has, 29.

we know the board has both high and low votlage, 120 and 29.

at control board:

1.) jumping r to g: fan will (should) come on.

2.) r to Y should bring on cool, inside blower and outside unit. if you jump this and ONLY the outside unit comes on than there's something wrong with the inside blower. It'd be highly possible the capacitor is bad. If nothing comes on then it's something else.

3.) jumping r to should bring on heat: the inducer (exhaust) motor should come on first followed by the ignitor or ignition coming on , then the gas valve opening, then flames and lastly the blower.

If when jumping anything and nothing happpens but the led light begins flashing a code, let us know what that code iw. And look for the legend which explains the code on any paperwork that came with the new board or else we'll be googling to find it.

Most likely during a call for heat (r to w) and the system is faulty is when a code will flash.

NickMN 06-25-2012 02:55 PM

I'll check when I get home , thank you very much for your detailed response.

Doc Holliday 06-25-2012 03:00 PM

You're more than welcome, that's why this site exists. :thumbsup:

NickMN 06-25-2012 10:40 PM

Just ran thru each test... Everything turned on per the sequence described. Fan right away, ac almost instant , heat in sequence!

Good to hear these components actually run!!

Where from here :)

Doc Holliday 06-26-2012 07:00 AM

Thermostat. Remove the cover to show the terminals which will be the exact same as on the control board. Check for those 29 volts between r and c.

Apparently all it was is the thermostat not receiving power. If it's a new stat and it's acting in the same manner as the old one meaning nothing happening then the lack of power is the likely culprit, broken or disconnected wire.

NickMN 06-26-2012 08:41 AM

Alright , I have since put back the old (2 year old Honeywell) after the filtrate thermo I purchased did not control the systems either. I will check out current setup & report back.

Thanks! Have a great day

NickMN 06-27-2012 05:54 PM

1 Attachment(s)
Attachment 53109

No c at the stat... I bought the same Honeywell model that was working and swapping that right now to try. 97 here in minneapolis , 80 in house. Thank goodness for good windows and blinds!!

NickMN 06-27-2012 07:09 PM

1 Attachment(s)
No response upstairs with new star, Connected with new wire to test. Nothing!! What gives :(

Attachment 53110

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