Came out to perform preventative maintenance on furnace for customer, but also inspect an issue he had as of yesterday. Customer stated that the system wasn’t turning on at all after yesterday when it quit working. I checked system over and found the 24v fuse blown. I did a thorough inspection of the low voltage wiring and found no issues in the wiring or thermostat kicking the system on. Asked customer if he’s used the AC recently and he didn’t recall turning it on, but his wife was the one home when it stopped working. I checked ac low voltage wiring and found no issues with the wires being tampered by the dogs. I checked resistance on the contactor coil after testing the ac and blowing another fuse, and found the contactor coil is bad. I discussed with customer about repair needed and customer approved repair. I replaced the contactor and tested AC again, low voltage fuse wasn’t going out anymore. I continued on with the furnace maintenance. I changed the filter for customer