Goodman Packaged Unit Troubleshooting

[lowe.joshua51]

I have a ng furnace/ac packaged unit and I went to use the AC for the first time since last summer and the blower fan came on but the ac compressor and the evaporator fan didn't come on. Obviously no cooling.

I did some testing of my thermostat wiring and all was good. I was getting 24VAC on the yellow wire from the thermostat.

I thought it might be the capacitor for the compressor/evap fan (it's the same capacitor for both) but that checked out.

I manually pushed in the contactor and everything came on and worked fine but I would have to sit there till it's cool enough inside.

Upon further investigation the contactor isn't getting 24VAC which is why it isn't engaging. The 24VAC line that leads to the contactor passes through the High Pressure Switch but there isn't 24VAC on either side of the high pressure switch.

I attached two pictures of the wiring diagram. The terminal I'm looking at is #12 that goes to the HPS then to the contactor. Does anyone know where the power for #12 comes from? There is no power on that connection.

I'm not experienced in these things but I'm decent at problem solving and figuring things out. This has me stumped though.

Thanks for any help you can give me!

 

[lowe.joshua51]

It appears that the pictures didn't load full resolution.

I found the wiring diagram here: https://www.acdirect.com/amfilerating/file/download/file_id/2513/

Page 28&29

 

[Climatecreator]

It probably comes from the board. Make sure the wire goes on firmly to the back of the Molex. Basically push the wire in directly AFTER the plug is plugged in, to make sure it "seats"

Does it have a manual reset button on the high pressure switch?

 

[lowe.joshua51]

It probably comes from the board. Make sure the wire goes on firmly to the back of the Molex. Basically push the wire in directly AFTER the plug is plugged in, to make sure it "seats"

Does it have a manual reset button on the high pressure switch?

Thanks for the reply. I'll try to unplug the molex connector and reseat it and push in the wire after plugging in the molex.

I just read about a pressure switch reset on another site so it's interesting that you mention it. I'll also look for that tomorrow; however, wouldn't there still be power on the pre-switch side even if the switch is 'tripped' (not sure the technical name)?

 

[Climatecreator]

Depends on how you're testing for power. If you're going ACROSS the switch and it's closed you'll see nothing. If you're going to ground then it's something you should see power to ground unless transformer is no good or board control fuse is no good or board itself is the issue.

 

[lowe.joshua51]

Depends on how you're testing for power. If you're going ACROSS the switch and it's closed you'll see nothing. If you're going to ground then it's something you should see power to ground unless transformer is no good or board control fuse is no good or board itself is the issue.

Great information, thank you. I tested from both sides of the switch, no dice. I also tested from ground to each side of the switch (seperately) and didn't have power at either. I'll do some more looking after work tonight.

I was able to get the house to cool down by manually tripping the contactor so it isn't 80 degrees in here.

 

[yeldogt]

Does it have a pressure switch -- could be low on refrigerant.

 

[lowe.joshua51]

Does it have a pressure switch -- could be low on refrigerant.

It does have a pressure switch, I don't think that's the problem yet because it isn't getting power at all to test.

If I understand correctly, the only way to be low on refrigerant is for there to be a leak or it was never filled correctly? I don't want to discount either of those but this unit is barely a year old. It was installed by the previous owner right before I bought the place.

 

[OzarkMan]

I would call the previous owner and find out who installed the unit. You should have a minimum of 5 year warranty through Goodman. Or call the realtor in the transaction.

 

[TRWham]

That unit has a high pressure switch to shut-off the compressor if the discharge goes too high, but does not have a low pressure switch for low suction pressure. That other pressure switch senses the gas supply pressure for the heat stage(s).

Check the voltage at terminals 11 and 12. If there is voltage at 11, but not 12, something on the board is open. I would guess it is the anti-short cycle time delay on the board that has failed. You could also jump from 11 to 12 to see if the contactor closes.