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Our ac would not kick on we was not getting 24 volt so we replaced the 24b volt supply and thrmostat and the only thing that will come on is the heat and nothing comes on on the ac side what could be wrong thanks
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Remove all the low voltage control wires from the thermostat, on the terminal board there is ,
R or Red = 24 volt "hot leg"
W or White = Heat circuit.
Y or Yellow = Cool circuit
G or Green = Fan circuit.
C or Common = 24 volt "neutral leg"
The R and C terminals are the 24 volt power supply, the R being the hot leg of power, C is the side of power that every 24 volt circuit terminates upon to complete the circuit.
Just as a car battery has a Negative post that all 12 volt circuits terminate upon in a car or anything electrical , they all require 2 legs of power, some voltages are only 1 hot leg 230 volts is 2 hot legs but 115 volts and 24 volts which a thermostat controls uses 1 hot leg being the R terminal.
The thermostat has switches internally that connect the hot leg of the 24 volt power to the desired circuit, jump red to white and heat comes on, jump red to green and fan runs, jump red to yellow and the AC unit outside runs. test this out and if it operates then the thermostat is bad assuming it is wired correctly.
On the ac unit electric section, check for power at Y1, should have power, possibly to x or c ( common terminal).
Check for power across the compressor contactor, should have power or something is open such as a pressure switch or compressor protection. If there is control power at compressor contactor solenoid ( 24 volts control), then check for supply power on line side of contactor, then on load side of contactor (supply voltage e. g. 230 volts. If all voltages are present, then check the compressor for opens and electric continuity.
CAUTION: electricity is dangerous, can kill and/ or cause fires. Do not attempt if not aware of safety procedures.
Gotta find where 24 stops. Possibly blown fuse, possibly losing your common. Check the 24 at relay to ground rather than both relay coil terminals to test common. Jump straight from transformer to relay to ensure that's what's happening.
You need to check to see if you have 24 volt signal from thermostat to your reversing valve. To go into cooling mode the reversing valve needs to be energized. Orange is normal color of the reversing valve power supply. On your unit will be a reversing valve which looks like a pipe with 3 pipes attached to one side and 1 pipe attached to the other side. On the side of the the reversing valve will be a coil with a 2 wire connection. This coil needs 24 volts applied to shift unit into cooling mode. In your thermostat wire bundle where it is connected, check for voltage between common and the orange wire. If it does not have 24 volts with the thermostat in cooling mode, you have a break in the line normally a connection on the orange junction inside your air handler or your thermostat orange wire is loose. Keep checking for 24 volts available until you find the source of the loss. If you have 24 volts at the reversing valve, you can check to see if the valve is working by unplugging the 2wire connection on the side of the valve, if it clicks its powered if not and 24 volts available then the coil needs replaced.
Any more than this you will need a professional tech to troubleshoot and fix.
Hope this helps.
If you have 24 volts at the transformer check the circuit board there is a 3 amp fuse on there its like a car fuse see if it is blown. Otherwise if you have 24 volts everywhere it has to be the t- stat because thats what kick the a/c on directly from t - stat. let me know
Hello. first thing to check is if you are getting 24 volts to the contactor coil, if not then the low voltage wiring needs to be checkd, if you are getting 24 volts to the contactor then and it is not energizing it must be replaced. Let me know what you find
Red or R is the "Hot leg" of the Transformers 24volt supply,
Common or C is the "Neutral leg" of the Transformers 24 volt supply;
and the side of power to which ALL the 24 volt control circuits
terminate to complete the circuit, example; Heat=W, Cool=Y, Fan=G.
Upon a call for heat a switch closes betwen the Red and White Thermostat terminals.
The stat sends the 24 volts to White or W for the heat circuit on W on the
furnaces LVTB low voltage terminal board.
Yellow or Y goes from Thermostat to furnace Y on LVTB, which is simply
a connecting point on its way to the AC units 24v contactor coil located outdoors.
It actually isnt even attached to the furnace many times as it serves no purpose there and simply
continues to the AC unit with the copper lineset that the AC unit feeds.
The remaing 24 volt Thermostat wire goes back to common on transformer to complete the Yellow
24 volt control circuit.
Green or G exits the Thermostat and connects to G on LVTB for the fan relays 24volt coil
and returns to Common to complete the Green 24 volt control circuit.
O is for a Heat pump reversing valves 24 volt solenoid, and return to Common as all 24v circuits must to terminate or complete the circuit.
Some parasitic type Termostats need the 24v power to run, some are battery, some are both.
I think you have a definite short and it's in the 24 volt circuit. The only problem is - 'finding a low voltage short' is not the easiest thing in the world to do - so - I would guess you'd need a Service Tech.
I am not familiar with this air handler, but I haven't found too many with fuses. You just blow the transformer... but if you found a place that says there is a fuse, maybe there is. If you can use a volt meter, check the voltage between the red and blue wire in the thermostat. It should be 24 volts AC. If it is there, your problem is something else... Some might suggest you use a short jumper wire from the red to the green and see if the fan comes on to check your 24 volts if you don't have a meter, but I would never suggest that... If you determine that the 24 volts is not there then you should find that transformer in the air handler and follow the leads out and see if they lead to the fuse, if it exists. You might consider that the transformer is bad if you can't find a fuse. If able, check the primary for your supply voltage, 115 or 230 volts AC, and the secondary, 24 volts AC. If your lucky, someone that is familiar with this model will answer with all the locations, etc... Always be careful when working with electricity. If you decide to get into the air handler to troubleshoot your transformer, turn off the breaker while exploring and only turn it back on when you are ready to make voltage measurements and are confident that you know what you are doing.
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