Question about Carrier Air Conditioners

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I have a Carrier 38tra048340 ac 4 ton unit outside, heater in attic. Thermostat is Totaline P374-1100. Power went out than back on after a few hours due to vehicle crashing into power pole. AC was running at time of power outage. Power came back on, ac would not come back on. Checked house circuit breakers, none tripped off. Turn ac 40amp breaker and heater 20amp breaker off and back on. Voltage ok. Checked fuse box by ac unit on wall, fuses and voltage ok. Went into hot attic to check for power up at heater unit, voltage ok. Amber LED light on circuit board says 24 volt circuit supposedly ok. Check voltage at digital thermostat, it reads 26.8 volts on all wire leads, R to C,G,W1,Y1, but thermostat screen is blank, nothing. Fuse on heater ac circuit board tests ok. I hear humming around the 24 volt stepdown transformer or the fan motor, not sure which. I see no burnt wires or markings. I push a switch in on circuit board, humming noise and amber led light stay on. Release switch, humming noise and led light go out. I need help with this one. HELP! thanks Jeff P.S. If you need Model# of Heater Unit, I will go back up into attic to retrive it.

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  • jeffandlaura Jun 25, 2008

    I accidently jumped r and c and blew the 3amp fuse on circuit board. I need to go buy another 3amp fuse at auto store and retest for 27 volts at the thermostat terminals c to r before I jumper r to g for fan motor start up and r to y1 for compressor start up. I just hope the fuse blew in time to save the circuit board and transformer. I will let you know after installing another 3amp fuse. be back soon, thanks, jeff

  • Anonymous Mar 15, 2014

    Have a 1996 Jayco Eagle 312 FK, looking for a wiring diagram, have no power to the A/C, Heater unit, fan... Have checked all breakers/fuses I can find all are good, have power going through the breaker but not getting to units? Is there some thing else some place I am missing?
    Thank you

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Blank screen sounds like a fried thermosat. Abrupt outages can affect certain types of thermostats. Make a jumper wire and jump across R and G. See if you get any action from anywhere. If a fan or compressor kicks in you know you have a burned out thermosat...

Posted on Jun 23, 2008

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