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Out door unit on a armstrong heat pump will not come on unit # SHP10B30A-2A using the thermostat, unit will come on by pressing in on the contactor.

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Have a look at the low volatage tranformer,should show 115 volts in and 24 volts out,when unit is calling for ac.There may be a small overload button on the side of the transformer,check that its pushed in.

You need low voltage to pull in the contactor.

Posted on Jun 06, 2010


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Need a wiring diagram for and armstrong SCU10A30A-3A AC unit specifically from the control board to the out side unit. not 24V to the contactors

Looks like all you have from inside unit to outside unit is the hot and common for the compressor contactor. What seems to be the problem?

Apr 12, 2017 | Heating & Cooling

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Fan stopped working on Armstrong Heat pump outside it hums. Model SHP10B364A-2A. If this is a capacitor please let us know what kind we can replace it with.

Replace the deal run capacitor that is connected to the compressor and condensor fan. The uf and voltage rating will appear on its surface. If markings cannot be read look for schematic inside unit to give you info - if nada, contact manufacturer for specification.of cap.

Mar 12, 2015 | Heating & Cooling

1 Answer


Generally, you would go from the thermostat to the air handler, and then, from the air handler to the outdoor unit. I don't know if you have a heat pump or not, so I will give you a simple diagram and you can contact me if you need more.

Thermostat : Y G R W and sometimes C
Air handler: Y G R W and C
Outdoor unit: two wires connecting to the contactor ( not heat pump)

Thermostat; Y--------------Y(air handler cooling)------------------one side of contactor, outdoor unit
G-------------G (air handler, fan)
R--------------R (air handler ,hot)
W-------------W (air handler, heat)
C--------------C (air handler, common)------------other side of contactor, outdoor unit

This is a typical wiring diagram. Just contact me if you have something different. Hope this helps. Stay cool. mark

Jul 10, 2011 | Heating & Cooling

2 Answers

My compressor doesn't turn on. My thermostat

you probably need a start/run capacitor. on the out side condenser unit. about $100.00 to have it fixed,

Jul 03, 2010 | Heating & Cooling

1 Answer

Outside unit wont go on ( central air conditioner)

Hi, yes when you hold down the contactor with a screw driver it will send high voltage to the unit and start up. What is happening is, on the lower sides of the contactor will be a 24volt coil, a wire to each side. You are not getting voltage to this coil for it to close the contactor on its own. If this system is central air with gas heat, you will have 2- small thermostat wires that tie to the 2- wires on the contactor coil. If its not gas fired, it will be a heat-pump with several wires coming from the indoor unit and thermostat. Either way, the 2 wires you need to worry about is the red and white or red and yellow for cooling coming out and connecting to the coil of the contactor, probably a blue and brown wire to each side. These are what closes the contacts on this. By using your finger it tells me you have high voltage there, that's good. If the indoor unit is running, the problem is either in the thermostat or the wires that come back from the outdoor unit to the indoor unit are not getting 24 volts. So, if the indoor unit runs, that tells me the transformer is good. Check the thermostat wire at the outdoor unit real well to see if it may have a break in the wires. If it looks good, go to the indoor unit and remove the control panel. There may be a panel switch on it that kills power to the indoor unit when removed and you may need to tape it down while you check things out. Just have it running when you pull the panel and if all stops, you will no.If it has a circuit board, look for a auto type plug in fuse 3 to 5 amp that may have blown. If you had a meter you could check the terminals at the 2 wires that head outside to start the unit for 24volts. If all looks good there, no broken or loose wires, go to the thermostat and remove the cover to expose the wiring. If its not a heat-pump and gas fired, you will have these terminals, RC, RH, with a red jumper wire across them, a G green for fan, Y yellow for cooling and a W white for heat.To see if the thermostat is to blame, take a piece of insulated wire and touch and hold it to either of the Red terminals and the yellow terminal. Have someone outside to watch the outdoor unit. If the stat is at fault, the contactor will close on its own when you jump the 2 terminals out. Make sure the indoor panel is in place first. I am almost certain this will be your problem since the indoor unit runs. If its a heat-pump, you will have more terminals at the stat. Still jump across the Red which is 24 volts to Yellow which is cooling. If the outdoor unit starts, replace the stat! This will solve the problem. Its just a matter of finding why and where you have lost the 24volt control voltage to the contactor coil to energize it, pretty easy if you follow my steps. It has to either be a broken thermostat wire at the indoor/outdoor/ or thermostat, or thermostat is faulty not closing R to Y to bring on the outdoor unit. Please keep me posted as I would like to know the out come. I am confident you can find the problem now that you know it is a 24 volt control problem not energizing the contactor coil. I will be waiting to hear back from you.

Jun 03, 2010 | Heating & Cooling

1 Answer

Goodman AC Unit with Heat Pump - Works great cooling when switched to heat the outside unit does not come on - inside comes on and uses emergency heat? What can I check? I first checked the contactor and...

Because the outdoor unit works in cooling, it sounds as though the contactor and other components outside are working correctly. The problem sounds as though it might be somewhere in your thermostat. Has the thermostat been replaced recently? If so, make sure it was wired correctly. If not, check all of the connections and contact points in your thermostat. In order for your outdoor unit to run, you must have 24vac at your "C" Common and "Y" connections. You must have this in COOL mode. Now it has to be determined why you don't have it in HEAT mode. Definitely a thermostat issue.

Hope this helps and good luck! :-)

Mar 05, 2010 | Goodman CKL60AR60 Air Conditioner

2 Answers


The outside fan may run if the unit is in defrost mode this is normal for most heat pumps it is there way of trying to keep the outside unit from staying iced over so the next time the unit runs it will have air flow through the coil and the ice will not be there to prevent air flow.

Jan 12, 2010 | Carrier 38CKC042 Air Conditioner

1 Answer

Armstrong Heat pump Package Unit, Model#1B36DA-9B,

Hi, the outdoor unit will start to freeze when it is cold outside, but also it should go into a defrost mode to melt this ice either by the defrost board or defrost thermostat. You will know as steam will rise like smoke and some folks think it is on fire. If it never goes into defrost, get back to us and we can go through some things to check. Merry Christmas,

Dec 24, 2009 | Heating & Cooling

1 Answer

No heat at night

You have a poor low voltage connection from the thermostat or a bad contactor.The contactor is the main relay control inside the condensing unit. The incoming voltage wires connect to it.
Contactors are inexpensive. I would change that first.
Check all your low voltage wires in the condensing unit for loose connections.

Dec 11, 2009 | Coleman Heating & Cooling

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