# AC problems.  Outside unit not kicking on.



## kcoughenour (Jun 2, 2016)

Hello all.  I just purchased my home, so dont know a lot of history behind the AC unit.  It is an American Standard Allegiance 10 and appears to be around 13 years old.  When I turn the unit on at the thermostat, the blower kicks on, but not the outside unit.  Ive done some troubleshooting and came to the conclusion that it is the main board that is not functioning correctly.  I will go into details if necessary, but the basics are:
Capacitor is good,
Contactor is good, but not receiving the 24 volts to activate it,
Transformer between the board and the contactor is not receiving any voltage from the board when the unit is running... thus my conclusion that the board may be bad?  

Can anyone give me some guidance on if I am correct in my thinking... and let me know of a way I can test the board?  I dont want to purchase a non returnable part if thats not the problem.  Thanks!


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## kok328 (Jun 2, 2016)

When you say your not getting voltage, are you talking about 120V or 24V ?


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## kcoughenour (Jun 2, 2016)

neither... I tested output side first and got no reading, so then tested  the 120v side by probing the connectors on the board that the transformer connects to and got no reading there either.  This was all done with the thermostat set to cool... the blower was running and the condenser unit should have been, but wasnt


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## havasu (Jun 2, 2016)

Bad capacitor. I know nothing about A/C but the last 4 services with my friends and family all had bad ones.


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## kcoughenour (Jun 2, 2016)

havasu said:


> Bad capacitor. I know nothing about A/C but the last 4 services with my friends and family all had bad ones.



its not the capacitor


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## kok328 (Jun 3, 2016)

If blower is running then I assume it's the thermostat telling it to run which means you have 120v and 24v. Sounds like a bad thermostat. Turn furnace off. Go to tstat wire nut red, green and yellow wires together. Turn on furnace. You should have indoor blower and outdoor compressor running now. If so then the tstat is bad or you had a bad connection at the tstat. Reinstall tstat. If no help, then replace it.


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## kcoughenour (Jun 4, 2016)

kok328 said:


> If blower is running then I assume it's the thermostat telling it to run which means you have 120v and 24v. Sounds like a bad thermostat. Turn furnace off. Go to tstat wire nut red, green and yellow wires together. Turn on furnace. You should have indoor blower and outdoor compressor running now. If so then the tstat is bad or you had a bad connection at the tstat. Reinstall tstat. If no help, then replace it.



Unfortunately I am out of town right now, so going by memory, but I pulled up a wiring diagram last night and it seems there is some screwy wiring going on.  I will be home later this afternoon to compare/confirm my theory.  I think I will try your suggestion first since it sounds easier and more logical though!  Thanks!


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