The 3 amp fuse blowing indicates some control function is either grounding out (probably a worn insulation on control wire) or one or more of the solenoid controls is pulling more wattage than it is designed to draw. The solenoids for the main contactor and reversing valves should only draw about 0.1 to 0.25 amp. Any more than this the solenoid overheats and causes the control fuse to blow. I have actually had to replace the thermostat wire on some units because the control that was pulling more than designed caused the entire length of thermostat wire to overheat and break down the insulation, causing the control wire to short to the common wire or others and cause more than required operations to occur simultaniosly. One unit had a short and emergy heat was coming on the same time cooling was on.
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The 3 amp fuse blowing indicates some control function is either grounding out (probably a worn insulation on control wire) or one or more of the solenoid controls is pulling more wattage than it is designed to draw. The solenoids for the main contactor and reversing valves should only draw about 0.1 to 0.25 amp. Any more than this the solenoid overheats and causes the control fuse to blow. I have actually had to replace the thermostat wire on some units because the control that was pulling more than designed caused the entire length of thermostat wire to overheat and break down the insulation, causing the control wire to short to the common wire or others and cause more than required operations to occur simultaniosly. One unit had a short and emergy heat was coming on the same time cooling was on.