Heating, Air Conditioning, Fridge, HVAC/5 Amp fuse blows in blower unit


My home has a Carrier model: fa4bnf048. My thermostat has no batteries, but lost power recently. I cycled the circuit breakers to no avail. I read that the blower unit may have a fuse that could cause this issue. So I checked and sure enough, I replaced it and the thermostat and heater worked fine for about an hour. Then the 5 amp fuse blew again. I replaced it with the thermostat unplugged and the breakers turned off. I turned the power on, then plugged the thermostat in. The 5 amp fuse burned out almost immediately (the thermostat came to life then died). Again, the fuse is in the blower unit in my attic. What can I do to prevent the 5 amp fuse from blowing? the circuit board in the blower unit says 5 amps also. Any help would be greatly appreciated. Thanks, Jeff


If the fuse blows almost immediately  as you state,I would remove all your low voltage wires at the air handler, marking them . You should have two set of wires one going to the outdoor unit other going to the stat. Then turn power back on to Air Handler . If fuse blows possible circuit board is bad or any type of time delay relay . Using a jumper wire jumper R to G terminal ,the blower motor should start. If so and fuse did not blow, try  R to G to W ,your heat should run. If all is well ,try R to G to Y your blower fan and outdoor unit should start. If this is a heat pump  jumping R to W to G will bring on your electric heat ( if you have a electric heat )  The number you provided was for a AH ( air handler ) ,what do you have , A/C with electric heat ? A heat pump ?  

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40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.


Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

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