I replaced the 3amp fuse on the control board. Started up the furnace. Heats OK, then the A/C, cools OK. This was on a Friday. Returned the following Tuesday (home is vacant & for sale). The fuse was blown. Replaced fuse again. And again, furnace/A/C started up and ran through a complete cycle.
Code 24 flashed in both cases. Says short in wiring or controller board problem (although that normally would be a code 45) No code 45 has flashed, just 24.
Seems the furnace works for a period of at least a few hours or more? before fuse blows again. Thermostat is in OFF position when fuse blows.
Any Carrier experts know what typically would cause this problem? No burnt electrical smells noted. Furnace is 8 years old. Has not been used much the past three years except in cold weather months and temp at 54 (home has been vacant). A/C hardly used the past three years.
The 3 amp fuse is there to protect your transformer from shorting out. when it blows it means you have a low voltage short in either your t-stat wiring to furnace or a short in the t-stat wire from furnace out to a/c, but the low voltage also travels through all your saftey switches in the furnace and the gas valve, so there are many possibilities. 1st place I would look would be out at the a/c and make sure the t-stat wire out there hasnt been hit with the weed wacker.