Curtis Reed Report post Posted January 14, 2019 Just seeing if any HVAC guys can steer me in the right direction. My air handler in the attic blew a 3 amp fuse. I checked for shorts in the air handler and condenser outside. Nothing obvious. The contactor looks good and I tested it. Got 14 ohms on the coil. I replaced fuse and if I run the fan only, the fuse is good. Once the stat is moved to HEAT and the condenser turns on the fuse blows. Any suggestions? Share this post Link to post Share on other sites
bonecollector Report post Posted January 14, 2019 Heat Pump? Share this post Link to post Share on other sites
PRDATR Report post Posted January 14, 2019 Post a picture of the wiring schematic and identify the fuse. 1 Share this post Link to post Share on other sites
Curtis Reed Report post Posted January 15, 2019 Ok thanks. It might take a while as i’m back to work. Share this post Link to post Share on other sites
muleybowhunter Report post Posted January 15, 2019 might be the transformer, or the thermostat, Share this post Link to post Share on other sites
TOBY Report post Posted January 15, 2019 reversing valve coil is first guess Share this post Link to post Share on other sites
Beaton Report post Posted January 15, 2019 Sounds like it could be the reversing valve. See if it blows the fuse if you turn the thermostat to cool. If it doesn't blow it could be the reversing valve. I am not an hvac guy but my reversing valve went out and it just wouldn't switch over to heat it wasn't blowing fuses. Share this post Link to post Share on other sites
TOBY Report post Posted January 15, 2019 The coil can be changed without the changing the valve. Hopefully its just that or a shorted wire that has rubbed to ground. Share this post Link to post Share on other sites
Curtis Reed Report post Posted January 15, 2019 Ok thanks i’ll check it out Share this post Link to post Share on other sites
PowellSixO Report post Posted January 16, 2019 Need a wiring diagram. Does your reversing valve energize in cooling or heating? Could be compressor contactor, reversing valve, or shorted wire. 1 Share this post Link to post Share on other sites
PowellSixO Report post Posted January 16, 2019 Find out WHEN the reversing valve energizes. Then put the T-stat in the opposite mode, and turn the system on. If the system runs without popping the fuse, then you will likely have a bad reversing valve coil. If it blows when just the compressor comes on (and the reversing valve is supposed to be off), then you likely have a bad compressor contactor. It could still possibly be a bad wire, but those are hard to find unless it's a hard short. If it's a hard short, go out to the condensing unit, and check for resistance on each of the t-stat wires to your copper refrigerant lines. Make sure to kill power to the inside unit, and the outside unit first. If you read any resistance to ground (copper refrigerant lines) on any of the t-stat wires, you have found your grounded wire. Share this post Link to post Share on other sites
Curtis Reed Report post Posted January 16, 2019 Thanks for all the help. I think it’s the defrost control board. I’m going to swap it out and cross fingers. When fuse is replaced and when unit runs briefly, it is stuck on aux/defrost mode 1 Share this post Link to post Share on other sites
Curtis Reed Report post Posted June 27, 2023 Thanks. The issue was worn out wire insulation causing a short. Share this post Link to post Share on other sites
verdehunter Report post Posted June 27, 2023 4 1/2 years later........I think it would be fixed in that amount of time. Share this post Link to post Share on other sites
Roosevelt Mark Report post Posted June 27, 2023 Thanks for the update, we were all wondering. 1 Share this post Link to post Share on other sites
