Heating, Air Conditioning, Fridge, HVAC/trane 15i heat pump


QUESTION: the automotive type fuse in the air handler blows whenever the out side unit is asked to come on. for a while before the fuse started blowing the compressor fan was running erratically. Emergency heat and air handler fan work good. Something is going wrong when the compressor tries to come on. Any ideas??


What I would do is remove all your low voltage wire hook ups at the outdoor unit ( first shut off power to the air handler ,as your low voltage power comes from the AH ) mark where the wires go. Start your HP in normal heat mode observe if fuse blows. If fuse blows you have issues with your low voltage wires in the wall ,the only thing that should run is your indoor fan. If fuse does not blow, add one wire at a time at the outdoor and run your HP each time shutting off the power to the AH.  ( make sure the wires you remove from the outdoor unit do not touch each other. Tape the bare copper ends.)  hook up the Y wire last ( that is your compressor contactor  ) if fuse trips you may have an issue with the control board outside,or if you have a control board inside . What does " the outdoor fan runs erratically mean ?? " your outdoor fan is controlled by the the outdoor defrost board. So if you have issues with your outdoor fan ,replace the outdoor fan. The outdoor fan either runs at top RPM almost instantly and the fan blade turns smoothly  ( normal operation ) Look at the wiring diagram to see what the fuse controls. Also double check the transformer taps to make sure you have the incoming voltage set correctly. If you have 210 volts at the AH your high side transformer tap should be set at 208 volt. If you have say 230 volt. at the AH you should have your transformer set at 240 volt tap. Double check for any burnt wire tips inside the AH or any lose connecting wires. Look at any relays at the indoor unit and outdoor unit for any burn marks on the relay body, which would indicate overheating of the relay coil. Remove the defrost board from the outdoor unit and check the back side for any burn marks around any resisters.

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QUESTION: What I mean by erratically is it slows down and speeds up noticeably and makes a bumping speed while doing so. Otherwise while it is not changing speeds it was running smoothly and quietly.
Thanks again.


looked at a XL15i wiring diagram ( you did not supply a exact model number, as they make a XR series also , 15i does not come up for me ) shows it's a single speed OD motor, should not slow down and speeds up.you can pull the two line voltage fan motor wires that go to the defrost board and tie together and tape the bare wires, and run your heat pump, if you notice the motor slowing down and speeding up ,your motor is going and needs to be replaced. if it does not slow down and speed up your defrost board may be opening and closing the normally closed contacts for the fan ( reason for the shift in fan speed )for a split second.

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QUESTION: Thanks again for your help.  I removed all wires and connectors in the compressor and turned on the heat pump and the fuse did not blow. so I started hooking up the wires one by one with the fan motor connector last. The fuse never blew again. The heat pump comes on normal for the first 30 minutes or so then the fan begins to struggle. eventually barely moving and making strange noises. Next I will try your suggestion of tying the to fan voltage lines together. There are 6 lines coming out of the fan motor. Black, brown, blue, white, yellow, green. Which two are the voltage lines? Is the defrost board the one with the flashing green light or the other one. I can read a schematic but there is no parts layout pictures.
         Thanks   Joe


Chances are the blinking lite board is your defrost board. Typical defrost boards have the low voltage wiring hooked to it, terminals O,Y,R,X2 OR W2,C, would be some of the hookups on the defrost control board. look at the wiring diagram at the outdoor unit ,there are no pictures layout just wiring diagram or goggle your model number and find an OEM defrost board to compare. Typically a outdoor fan motor only has 3 or four wire leads. The green wire is the ground wire.just because you have 5 wires (minus the ground green ) does not mean all wires are used. You would have to look at the wiring diagram to see where each wire goes. one or two are probably not used and hook to a dummy terminal or are hot hooked.To me your describing a bad outdoor fan motor that pulls air across the outdoor coil. ( compressor ) not to be confused with the indoor blower motor, yes? you could try changing the capacitor first, ( your capacitor probably has a three terminal hook up,the other hook up is for the compressor, called a dual capacitor ,depending on age of your unit you could have a dual capacitor or a single one dedicated cap. for the outdoor fan motor ) but it sounds like the motor.trace back one of those motor wires and it should go to the board coming out of the board the other line voltage wire goes to your 220 volt power somewhere.The wiring diagram should show that. If your wiring diagram is faded ,goggle your model number to get a better layout. Color of motors do not mean alot , different manufacture may use different colors.the brown wire should go to the capacitor.With the amount of wires you have ,sounds more like a indoor fan leads, as a multispeed indoor blower motor has several speeds and use that many wires.

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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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