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We just returned home from a week's vacation to find our Trane…

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We just returned home from...
We just returned home from a week's vacation to find our Trane thermostat blank. The upstairs one is working fine. The air is not running downstairs. There were electrical storms while we were away. Any suggestions? We have flipped the breaker, just to check.
Submitted: 3 years ago.Category: HVAC
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Answered in 2 hours by:
7/3/2015
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
hvacexpertjoe
hvacexpertjoe, HVAC Technician
Category: HVAC
Satisfied Customers: 183
Experience: I have owned and operated 2 HVAC companies in KY an WV. My background is electrical engineering.
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If the display is blank you could have A: Dead batteries in thermostat. B: Fuse is blown on indoor units printed circuit board. Look for the circuit board on inside unit and should be a flat 5 amp fuse on circuit board that has burn marks on it. Could be mounted to indoor units fan housing.To test thermostat you can run a jumper from the G(green wire) to the R(red wire) after removing the thermostat from the wall. This will turn the indoor units fan on. If this occurs yo may have a bad thermostat.
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Customer reply replied 3 years ago
I don't see any regular batteries in the thermostat. Would they be a special type of battery, or could that mean it's getting power through the wires?
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
No, AA or AAA. If no batteries try removing the thermostat and jumping the G to the R terminal with a small piece of wire. The fan on the indoor unit should kick on. If it does you have a bad thermostat. If it doesn't you may need to check the fuse in the air handler.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
No batteries means the thermostat is powered by the air handler.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Things to check in the air handler are the fuse and the door switch. After checking the fuse on the circuit board make sure the door is securely closed. Sometimes this will keep the unit from powering up.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
So this looks like a zone controller to me. It appears that the thermostat to one of the zones looks like it is not working. Are you able to take a thermostat from another zone and plug it into this zone to see if it is a bad thermostat?
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
The pictures are kinda blurry but it looks like you have 2 thermostats and the thermostat to the uncorking zone looks as though it has a red LED on showing that it is powering the zone thermostat but the G and Y are not lit up. The other zone the G and Y are lit up. So it appears that the controller is powering the thermostat but the thermostat is bad. My money is on a bad thermostat
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Sorry not uncorking.....non working zone
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
The only other thing I can think of is to power down the air handler and zone controller and see if it comes up after restoring power.
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Customer reply replied 3 years ago
We did have an electrical storm while we are gone. So maybe the powering down/restore is worth a try, before we buy a new thermostat. Can you walk me through that?
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Powering down air handler. 1. follow large power wires from air handler they might go to a breaker. Pull the cover doors off the air handler it probably has a door switch to power it off, or go to the main home breakers and look for the breaker labeled on the chart as air handler.
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Customer reply replied 3 years ago
I turned off then rebooted both air handlers. No dice. Traded thermostats. Still isn't working. I'll send a picture of the inside of the wall portion of the thermostat. There's some black stuff around the opening. Didn't know if that might mean something to you??
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Do you have a voltmeter? There should be 24 volts AC between the R and B at the thermostat. If the other thermostat didn't power up either it sounds like you don't have power to the wires at the thermostat. Check and make sure the R and B connectors at the zone controller have a good contact. You may try releasing the R and B wires at the zone controller by pushing the orange tabs with a small screw driver and re-seating them.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
At this point I am suspecting this. The red LED at the zone controller being on is telling me that 24 volts AC is going out of the "R" connection on the zone controller. IF 24 volts is making it to the thermostat it still needs the "B" connector as a 24volt common. Maybe 24 volt common or zero volts is missing at the zone controller because it fried a solder connection? You could try running a jumper between "B" on the the other terminal strip at the zone controller. So a jumper between "B" and "B". My other guess is that the thermostat wires in the walls have been burnt in two.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
This doesn't look abnormal to me. Sometimes airflow through the wall cavity blows through these holes and dust collects here.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Smell the hole. Does it smell burnt?
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
Do you have a voltmeter possibly?
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Customer reply replied 3 years ago
It doesn't smell burnt. My husband says it looks fine to him.Sounds like my husband and I may be above our pay grade. : ) Do you recommend that we call an HVAC guy, or electrician? Thanks for all your time.
Customer reply replied 3 years ago
We don't have a voltmeter.
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
If we don't have a voltmeter troubleshooting at this point would be difficult. I think we have taken care of any easy fixes and at this point I would recommend getting a tech to come out.
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HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
HVAC tech definitely
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Customer reply replied 3 years ago
Thanks so much!
HVAC Technician: hvacexpertjoe, HVAC Technician replied 3 years ago
your welcome. Best wishes!
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