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justplumducky 09-18-2013 07:51 PM

Blower not running - Package unit, A/C & Gas Heat
Blower motor not running (currently using Cooling function of this system). Blower motor would not come on when Heat function of unit was turned on - burners shut down after a couple minutes or so. Fan ON switch at t-stat would not turn blower motor on either.

13 year old A/C and Heat package unit, Model # DAYA - F030N070C (York, possibly?) Control board Model # ST9120C 2002 Edit: this attached pic is the best pic I could find similar to, or same as, the currently installed board. Model # of attached pic is ICP-1170063. Attachment 75981

Recently, new contactor, blower motor & run cap (also dual run cap). of proper spec (10 uf).

After a quick check of wiring and transformer, contactor voltage In and Out, 24vac input at board terminals, I removed the blue lead from board's Cool terminal (med speed, per wiring and connected it to what was possibly the L2 side (input/supply side of contactor/L1/other side of contactor was also connected to blower motor). Blower motor started right up and compressor no longer began to ice up and system started cooling normally.

Green light on the board was pulsing, indicating normal operation of board. Could this be anything other than a control board failure? I didn't think, until now, to look for a bad fuse (was probably under a black, snap off cover on the board, covering the relays and whatever else). But when turned to heat function, inducer motor started right up and that's controlled by the board, correct?

If it is a control board failure, no problem to leave the blue lead ( removed from Cool terminal on control board) connected to contactor overnight or for a few days? Blower motor would run continuously until I get the new control board - or should I have connected the blue lead to the output side of contactor, which then would run blower only when t-stat calls for Cooling (as long as t-stat is left in Auto/Cool position...?

Thx much for any help.

Doc Holliday 09-18-2013 08:46 PM

not a control board failure, an idiot attempt at repair failure. there is no one board fits all. but all you need to do is check voltage from the board to the motor to see if indeed the board, not the exact same replacement mind you, has power being sent to the board.

check hot tap pf board to any ground upon a call for whatever. also, was the motor that was installed the exact same or was it generic replacement, a multi tap hp motor? was the right tap used and on those replacement motors the cap size changes...

justplumducky 09-18-2013 09:17 PM

I didn't check the motor label for run cap specification, but the replacement was done by a certified and long time (20 yrs + or more) HVAC tech. It was a universal multi-speed tap motor with blue connected to Cool terminal of board, for medium speed (smaller mobile home, if that's the reason for blue, instead of Black for Hi speed?). Red was connected to Heat for low speed (both connections were per wiring diagram on inside of electrical panel cover).

I did see some notes where the original board was replaced a long time ago - have forgotten now just how long ago.

I removed blue lead from Cool terminal and connected meter to that terminal and ground - got about 1 volt. So, you're saying what I missed and need to do now, was making sure there's 120v to board, correct?

Please explain the "pf" part of ...("check hot tap pf board to any ground upon a call for whatever").

Wouldn't there have to be 120v to the board for the inducer motor to run?

I don't know if it really makes any difference or not, but I may have mis-led, about the model number of the board, in my opening post. The model number I gave, is indeed, the model number of the currently installed board ( which is, however, a replacement for the original board, but don't know what board that would have been). The attached pic is model number ICP-1170063, which is the best pic I could find , similar to or same as, what's currently installed. Sorry for any confusion (if there was any). I have edited my original post to clarify that, if it makes any difference.

If I'm wrong about the inducer motor starting up because its 120v's comes from the board, and in case I have any trouble with identifying, per the wiring diagram (maybe not legible for that part of it), the terminal on the board to check
for 120v input to the board, could you please identify that terminal on this attached pic?

Thx for your help.

justplumducky 09-19-2013 11:45 AM

Ok, I realized that this board replacement involves the gas appliance side of this system also, so I've decided to have a pro do it. Thx for the input.

justplumducky 09-22-2013 07:13 PM

It was, indeed, a control problem. The board had a burned spot (solder connection) directly underneath the board's indoor relay -

We replaced a Honeywell ST9120C 2002 control board, with a Honeywell ST9120U 1011 universal control board, actually labeled Honeywell Electronic Fan Timer or something like that (the new board I mean).

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