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Discussion Starter · #1 ·
The fuse on integrated control module in a goodman model GMT blows almost immediately when replaced in the AC mode. I have check the 120/24 transformer with an ohm meter and it reads no short to ground on either side and the opposite poles are isolated. The board shows no "burned" components or spots from the front. Are there another tests that I might do before replacing this module?
 

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The thermostat wiring to the outside unit may be damaged by weed whacker/dog/rodents. Check it first. Then remove it at the unit outside and try turn unit on. If it still shorts then the short is in the wiring to the house or the furnace and not the outdoor unit. Look for dead mice, bad contactor in outdoor unit.
 

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Check the control wire to your outdoor unit. Animals and weed eaters commonly damage it.



The control wire can also rub against copper pipes in the outdoor unit and cause this problem.
 

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Discussion Starter · #4 ·
Thank you for your quick feedback. I did what you suggested and I also disconnected the ac unit contact solenoid from the control mod and tested to see if the fan would come on and it did. Then reconnected the outside solenoid and it blew the fuse again. The contact solenoid does show discoloration by not that bad and it read out ok, but I do not have a megger.
 

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You don't need a megger just a new contactor from Graingers (under $50). They are rated in amperage draw for the contacts but I would get a 30 amp one as it is the largest and has better contacts. It is probably mechanically seizing and drawing too many amps not necessarily shorting.
 
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