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View Full Version : 5A fuse breaking, contactor and reversing valve solenoid shorted


Tefs1
Jan 9, 2011, 07:56 PM
Hi everyone, I appreciate any help you could provide, I'm going to give as much back story as possible to try and make my situation clear.

I own a home in north Florida and have been running the heat for a few months now on and off.

On Saturday morning I woke up to find that the thermostat was blank. This has happened in the past due to the condensate line filling with water and activating a float switch that shuts my system down. I found this wasn't the case, so next I checked the 5A fuse in my air handler and found it broken. I replaced the fuse, the system worked for a few minutes with the inside unit fan on, until I switched the system to heat and the fuse blew again.

I check the 24V circuit for shorts with a meter at my thermostat and found the C, O, and Y wires to be short to one another. I went to the outside unit, disconnected these lines, checked the thermostat again and these wires were now open to one another. I believe this narrows my search to the outside unit.

I disconnected the contactor and reversing valve solenoid from the main circuit board, checked and found no shorts on the board. I removed the two wires from the board to the contactor and found the coil resistance of the contactor to be near 0 ohms, I suspect this piece is in need of replacement.

I checked the resistance of the two wires from the board to the reversing valve solenoid and again found the resistance to be near 0 ohms, I suspect this piece also needs replacement.

Finally I left the outside unit controls unplugged from the thermostat, and with a new fuse the unit is able to heat on EMHT.


Does it seem as though these two pieces need replacement at the same time? I am suspect because I don't know that they have anything to do with one another and I don't understand why they would both go bad at the same time. I have checked the wiring on the outside unit from the access port, but not internally by the reversing valve, is it possible that the wires themselves could be shorting and causing my problem? Are either of these pieces very difficult to replace, I like to think of myself as pretty handy, although that can sometimes get me into more trouble.

Thank you in advance.