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Old 06-05-2010, 05:42 PM   #16
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replaced thermostat....nothing, need help please


You may have a dead short in the tstat wiring and to the outdoor AC unit which then drew too much current and melted your tstat.
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Old 06-05-2010, 07:42 PM   #17
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replaced thermostat....nothing, need help please


I am replacing the thermostat wire tonight. Will post the results. If this isn't the culprit, what remains? Circuit board, what else? It appears I have power going to AC outside but no power coming back in from AC? What actually supplies power to circuit board?

Thanks for all the help and sorry for all the dumbness on my part!
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Old 06-05-2010, 08:44 PM   #18
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replaced thermostat....nothing, need help please


Had one a month ago the high pressure switch shorted out, it was a Amana
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Old 06-05-2010, 08:50 PM   #19
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replaced thermostat....nothing, need help please


Here is the BASIC operation:
1) Power enters furnace thru door switch. Check if it is getting thru the door switch with the switch pressed in
2) Goes to the 110 to 24 volt transformer. Check if 110 is at the primary side of transformer and 24 volts coming out the secondary side. If there is 110 in but no 24 out then the transformer blew and you need to find out why.
3) 110 goes to the circuit board thru the wiring harness and that is likely beyond your skills as it needs to be traced from the wiring diagram etc. 24 volts also goes to the board and should be at the R terminal. C is the return to the transformer.
4) Normally the fuse blows before damage occurs but you have something strange going on. Check the tstat wiring to the outdoor unit to see if it got damaged by weed whacker/dog/rodents chewing it.
5) The fuse on the board should be no larger than 5 amps
Don't panic, lots of Pros and talent here and we should be able to narrow the problem down for you and educate you
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Last edited by yuri; 06-05-2010 at 09:08 PM.
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Old 06-06-2010, 03:09 AM   #20
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replaced thermostat....nothing, need help please


Door switch closed and no voltage between r & c on the control board? how many volts between sec1 and sec2 terminals on the control board? If you suspect the control board is the faulty component, can you take it out and inspect the underside? Burn marks are a pretty good indication that the board is faulty... As Yuri mentioned, the guys here are pretty bright. They can walk you through this.

It's pretty strange that your t-stat melted.
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