Tip & How-To about GE APH10AA Air Conditioner

How to Trouble shoot Low Voltage Controls on AC-Heat

What I have always been told is if your 24 volt side burns out check the high volt side if the hi volt side burns out check the low volt side.

A quick way if the primary side is burning out due to a problem with the low volt side:
1* Mark all the thermostat wires at the indoor unit.
2* Disconnect them at the indoor unit.
3 Check main line voltage before proceeding (A on electric furnaces, 208 volt is not considered 220V and 240v Is not considered 208V. In these circumstances the voltage may have changed with the power company replacing a transformer and now you need to change the main power input lines at your control transformer for the correct operating voltage). If OK then proceed:

4 If you have an amp meter attach it to one of the lines going to the transformer.
5 Apply main power and listen for hum, note if smell starts again and if so problem has to be in board or main incoming voltage too high or too low. Amp draw should be less than 3 amps.
6 If your to this point and still haven't found any trouble in the above as of yet, Connect the wire marked "C" together. Then just touch the thermostat wires one at a time to the places where they go on the indoor unit and watch the amp meter. If you don't see the meter jump the circuit is probably OK but leave them disconnected until you touch all of them to the correct place or wire. Here is a possible problem I have seen a thermostat wiring problem if the wires are stripped too far and a "whisker" of the wire sticks out and allows one of the other wires to cross short out. In this case just cut off the excess wire or bend it over out of the way and continue with the test. You can always cut it off later after the tests. If you see the meter jump up and stay up and /or blows the fuse the wire that you used and it blew is where to concentrate.

(* you may need to reattach the wires at the indoor section then disconnect them at the Thermostat and then at the out door unit if you have not discover the cause at this point or after finding the wire(s) that cause the Spike on the AMP meter. Just take your amp meter with you and reconnect the "R" wire first and check it first. after that if nothing shows at each place connect the "R" back and proceed with touching each other wire individually while amp reading the "R" wire).

7 No wiring problem found means that you could have a relay or contactor not pulling in properly.
and this will cause the amp draw to go way over the transformers power out put or VA rating.
8 Inspect the thermostat wiring for the "whisker" I mentioned above.
9 If you have done this to the end of the thermostat wires and your main incoming voltage is correctly wired in on the transformer and your relays and contactors are pulling in evenly and not delaying excessively your problem should be fixed.

If this helps you please rate me as high as you can and thank you for using fix ya.

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1 Answer

not getting 24 volts out of transformer to furnace valve why


isolate transformer and check voltage on both end of transformer,

disconnect power and with om-meter check for resistance on high voltage side as well as on low voltage side, check for bridging between the sides and between the chassy and sides. resistance on both sides should be very low, resistance between low and high side and chassy should be very high.

if resistance as described - transformer is ok.

check valve and layout, on layout you should have resistance/voltage points and therefore check them if they are valid.

hope this will help, do not forget to vote...

Jan 01, 2015 | Heating & Cooling

1 Answer

carrier central unit outdoor unit will not activate .i have replaced the voltage transformer inside , and the positive contact in the outdoor unit . my local ac man told me that i may have a problem with the common ground.


Hi, I would say to check for high voltage at the outdoor unit. You will have 24 volts from transformer on the secondary side of it, and high voltage on the primary side of the unit. @4volts are for all of the controls on the unit, contactor coil, all of the safetys, pressure switches high and low Ect. On a call for cooling, the stat sends power to the contactor coils, 24 volts to energize it and close the contacts and in turn starts the fan and compressor. Make sure you have high voltage at the unit. If not, check the main breaker, or the box mounted at the unit. Most will have 2 fuses in them that are behind a plastic cover. You can ohm them or just replace if your not sure. If you have power. If this is a split system central unit, check at the contactor for high voltage. If you have it, and it will not come on, you have to see if you are getting 24 volts to the contactor coil to pull in. If it does not, the problem is in the indoor unit unless this is a all in one outdoor unit. Please let me no, give me the details please.
Sincerely,
Shastalaker7

Apr 16, 2010 | Heating & Cooling

1 Answer

how to connect a thermostat to heat source. bought thermostat to work in a homemade incubator. i can power in unit but when i connect heat source(light bulb) it wont switch it on when temperature is below bottom.need help. thanks. eoin


get yourself a RIB (relay in a box) relay that is rated at 24/120. Also purchase a 24 volt door bell transformer. Wire 2 24 volt thermostat from one side of the transformer to the low voltage side of the relay then to the 24 volt thermostat than back to the other low voltage wire of the transformer. On the high voltage side, from your light bulb cut the wire going to the center lug of the light. Run one side of the wire to one side of the high voltage side of the relay, then run a wire from the other side of the relay (again high voltage side) to the the other side of the wire you cut on the light.

Mar 08, 2010 | Heating & Cooling

1 Answer

CARRIER AIR CONDITIONER/HEAT PUMP PROBLEM WOULD NOT RESPOND TO THERMOSTAT. UNIT IS AT LAKE HOUSE WHERE WE DO HAVE BAD STORMS. IN CHECKING, INSIDE PART OF UNIT HAD BURNED UP THE TRANSFORMER BUT NOT BLOWN THE FUSE. REPLACED TRANSFORMER . . . COULD SMELL AND THIS TIME TRANSFORMER STARTED TO MELT AND BLEW FUSE. SOMETIMES THE FAN WOULDN'T EVEN COME ON WHEN JUST SWITCHED FAN "ON" AT THE THERMOSTAT. QUESTIONS: WHAT WOULD KEEP BURNING UP TRANSFORMER. WE REPLACED WITH EXACT TYPE THAT WAS ORIGINALLY ON UNIT???? THANKS


what I have always been told is if your 24 volt side burns out check the high volt side if the hi volt side burns out check the low volt side.

A quick way if the primary side is burningout due to a problem with the low volt side:
1 MArk all the thermostat wires at the indoor unit
2 Disconnect them at the indoor unit.
3 Check main line voltage before proceeding (A 208 volt is not considered 220V and 240v Is not considered 208V> In these circumstances the voltage may have changed with the power company replacing a transformer and now you need to change the main power input lines at your control transformer for the correct operating voltage). If okj then proceed:

4 If you have an amp meter attach it to one of the lines going to the transformer.
5 Apply main power and listen for hum, note if smell starts again and if so problem has to be in board or main incoming voltage too high or too low. Amp draw should be less than 3 amps.
6 If your to this point and still havent found any trouble in the above as of yet, Connect the wire marked "C" together. Then just touch the thermostat wires one at a time to the places where they go on the indoor unit and watch the amp meter. If you donmt see the meter jump the circut is probably ok but leave them disconnected until you touch all of them to the correct place or wire. Here is a possible problem I ahve seen a thermostat wireing problem if the wires are stripped too far and a "whisker" of the wire sticks out and allowes one of the other wires to cross short out. In this case just cut off the excess wire or bend it over out of the way asnd continue with the test. You can always cut it off later after the tests. If you see the meter jump up and stay up and /or blowes the fuse the wire that you used and it blew is where to consentrate.
7 No wiring problem found means that you could have a relay or contactor not pulling in properly.
and this will cause the amp draw to go way over the transformers power out put or VA rating.
8 Inspect the thermostat wiring for the "whisker" I mentioned above.
9 If you have done this to the end of the thermostat wires and your main incomming voltage is correctly wired in on the transformer andf your relays and contactors are pulling in evenly and not delaying excessively your problem should be fixed.

If this helps you please rate me as high as you can and thank you for using fixya.

Apr 24, 2009 | Heating & Cooling

1 Answer

How to test for 24 vac between R and C


Yes you are right the control voltage of your furnace is 24 volts. Really without a load on the transformer usually runs 28 volts then you put a load on it and it drops down to 24-26 volts. Check the voltage between the R terminal and the W terminal with the selector switch in heat mode. Or move the thermostat switch to heat. R to C would do it also. You could also do the voltage check right at the transformer one side of the transformer is 120 volts and the other side is 24. Look for the black and white wires that is the 120 volt side the blue and yellow or off colors is the secondary side.

Now if it checks low say 24 or 22 your gas valve needs min. 24 volts to hold open the valve that allows the gas to flow into the burners. So if one of the symptoms is related to burners come on for about 3 to 5 min. then shut down and the fan keeps going it is loosing the necessary voltage to hold open the gas valve.

One more thing make sure the air filter is clean as this will cause the heat to build up in the heat exchanger and hit the high limit safety device and cut the gas off. Until the air cools enough to allow the high limit to reset then the gas valve will open and start the process all over again. Dirty A-Coil will do the same thing as the air goes through the coil to get to house. let me know how it goes ken

Jan 18, 2009 | Heating & Cooling

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