# No power at thermostat/i think i blew a fuse



## marcpilot1 (Jan 16, 2014)

Hi everyone. If anyone can help me I'd be sooo much thankful, appreciative. I have a Trane xl12 heat/cooling unit. A Trane tweo24p 130b0 air handler. And the thermostat is a trane T8411R. All of the equipment is about 8 or 9 years old maybe. 
   Yesterday I lost the display on my thermostat screen and called 800 #. They asked a few questions, said the display couldnt be fixed, to go get this other new one from lowes or home depot. Now, the thermostat would still heat and cool, I just had no way to see what the temp setting or anything was to control it right.
    So I go get the thermostat they said to get. Install it exactly right, very careful, stickers on each wire, one at a time, just very meticulous. Well, after I turn on the breaker nothing works. I try a few things, nothing, so I call 800 #. They ask a few questions again, get letters off the wires and so on, then say I installed the wrong thermostat, to go get this other model and that one will work with my system. Well I only installed the one THEY said to install. So I'm screwed I figure while he's saying I probably blew a transformer or fuse at air handler, the breaker or somewhere else. All this in an accent I could barely make out! I was livid and couldnt understand what they werte saying to me. 
   So anyway, thats where I'm at and if anyone knows or has any idea what to do, I will be forever indebted to you all to say the least. Thanks a lot!, Marc.  (the wrong thermostat was model #RTHL111B and the correct one that goes in there is model # RTH3100C) Thanks again!!


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## kok328 (Jan 16, 2014)

On the side of the furnace there should be a light switch.  This is the 'service switch' to the unit, when this is off, there will be no power in the unit and is also a handy way to 'reset' your unit when it errors out.
Turn this switch off.  Remove the metal panels on the front of the unit and find the green circuit board.  Somewhere on this board you will see a yellow? 4 or 5 amp blade style fuse (the kind they use in cars).
Pull this fuse out and see if it is good or not.  Replace as necessary.  P.S. - buy a couple while your there, there is a good chance that something is blowing the fuse.  Could be a bad hot surface igniter drawing too many amps.
For anything else, you'll need a volt/ohm meter to troubleshoot the system.


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## marcpilot1 (Jan 19, 2014)

Kok328, you nailed it. And the fuse was right in the direction you pointed me. I replaced it and it blew as soon as wife flipped on the breaker. So I went back to the thermostat and moved a wire to the correct terminal and bam, it didnt blow when she flipped the breaker on this time. 5 mins later, heat was coming out of the vents. I was so thankful. It took me a couple days to get back to you all as after everything got back to normal around here, I forgot. But I remembered today and wanted to make sure I thanked the whole site here. You and the website are exactly what I needed and I still cant thank you all enough, Marc.


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## kok328 (Jan 19, 2014)

your welcome and thank you for coming here and allowing us to help you.  if there is anything else you need help with; you know where to find us.


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