Hey all, new to the board, question about my HVAC

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Hey all, new to the board, question about my HVAC

Postby canadianlad » Wed May 28, 2014 1:15 pm

I have a furnace, central air. When winter hit the heat wasn't working, the furnance burners wouldn't turn on though the fan would blowing dry air when set to fan and when set to heat above room temperature the fan would kick in, but again, no burner so no heat. I bought a new thermostat, installed it and as luck would have it the furnace burners kicked in and all seemed fixed.

Now it is summer, we need the AC. I switch the thermosta to cool and the outside unit doesn't turn on, what's more odd is that the furnace won't even blow dry air when on fan, the fan of the furnace only works when it is set to "heat". So, when set to cool, fan won't work on it's own and no A/C, when set to heat, fan and heat turn on.

What could be some troubleshooting issues here? I would logically assume it has to do with the wiring, but I don't want to mess with the thermostat unless I need to there is not alot of wire to access and it was a sob just to wire it up the first time. So, I am looking for an array of suggestions if you have them.

Thanks in advance. Cheers.
canadianlad
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Postby Freon » Fri May 30, 2014 3:15 pm

What make and model thermostat?
When you call for AC, go outside and listen to the condenser. Do you hear a hum? That hum, if you hear it, would be the contactor.
Are the thermostat wire colors you see at the thermostat connections (R, G, Y etc) the same colored wires you see at the corresponding connections points (R, G, Y etc) at the furnace control board?
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- Hey all, new to the board, question about my HVAC

Postby canadianlad » Sat Jun 21, 2014 12:14 pm

Hey Freon thanks for the help.

Sorry I didn't respond sooner, I wasn't in town. Hopefully you are still able to provide some advice and I hope i give you enough information to work with.

The Thermostat is a Honeywell. I don't know the model numebr but it is a basic thermostat with a white vertical face. One of those cheapie jobs, choose hear, fan or cool, choose your temperature. Hold temperature.

When the AC is supposed to kick in I do not hear a humming sound emitting from the condenser.

As for the wiring; which is my guess where the problem lies but also the problem I least want to address due to concerns I will have heat problems in winter again which is far worst than AC problems in summer where I live.

Regardless, I am not a furnace or electical expert obviously but I see wiring on the furnace board lined from left to - R C Y W G, configed as - R- Red, C- Yellow, Y- Yellow, W- Black AND grey ( assume one of them is the ground or neutral?), G- Green.The C and Y both have yellow wires further confusing me. The furnance is about 7 years old.

The therostat has only 4 wires available to connect though 5 slots on the thermostat (Y, G, Rh, Rc, W). The config is as - Y- has blue wire connected, G- Green, Rh- Red, Rc- NO WIRE CONNECTED, W- Yellow Herein must be the problem as there does not seem to be Is there a specific config you would suggest to get the A/C going? Obviouslt the allignments are out of wack, but how can I match when I don't have the same number of wires on the thermo? Furthemore the furnance board has two yellow lines confusing me even more.

Thanks for anything you can add here pal, from what I see you are a great asset to the board. I appreciate your patience.

Cheers.
canadianlad
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Postby Freon » Sat Jun 21, 2014 1:59 pm

You wrote, "When the AC is supposed to kick in I do not hear a humming sound emitting from the condenser. "

The above tells me the condenser is getting the signal to run from the thermostat. The humming you hear is the 24 volt contactor controlled by the thermostat that switches the 240 volts AC to the fan and compressor.

Check the 240 volt power to the condenser. Check circuit breakers for the condenser. Possibly the contactor points are shot. Possible the run capacitor is bad. But from what you said it seems the thermostat is doing its job
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Postby canadianlad » Sat Jun 21, 2014 2:18 pm

Hey Freon,

So just to clarify, I do NOT hear a humming sound, so this means the condenser IS getting the signal?
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Postby Freon » Tue Jun 24, 2014 2:37 pm

My mistake... it seems the condenser contactor in NOT getting the 24 volt power.

Try this experiment. Turn off the power to the furnace. Remove the thermostat cover so you see the base where the control wires from the furnace connect to the thermostat. DOUBLE-CHECK that the same wire connected to the thermostat R terminal is the same wire connected to the R terminal at the furnace control board. Check that all terminal connections (Y,G, etc) are solid and the wires are in good condition.

Once you have verified the control wiring, then at the thermostat with the furnace power still off, make a wire jumper between the R terminal and the Y terminal at the thermostat. You are now calling for the AC to operate. Now turn on the power to the furnace and go outside and see if the condenser is running. If it is, then your problem in the thermostat. If it isn't, listen for a hum from the condenser contactor. If there is no hum we will look elsewhere. Go back and turn off the furnace power and disconnect the jumper.
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