Transformer keeps going out on a 24B AC-unit-furnace Carrier 48XPN.

Transformer keeps going out on a 24B AC untit/furnace Carrier 48XPN. Client calls Sunny Appliance Repair to have a tech come and take a look at his AC unit. When the technician got there he ask to point him toward the unit, thats when he discovered it was located on the roof. He client gladly provided a latter. Once up there he was able to see a big furnace/AC unit(2 in 1) Carrier48XPN. Technician opened the lid to inspect, first he checked that there was power going to contact 240B. He did that to insure everything is ok with the safety switches. Next he star examining the control board- which was not functioning at all due to a bad case connection to 24B. Next he examined the transformer which had power coming from 240B, but there was no outgoing power to 24B. Turned off the power to 240B took off all wired going to the transformer and started testing it- first coil for 24B.

Which showed continuity and 240b did not, witch means the transformer burned out. Technician replaced the transformer, at witch point the control board started working properly. Thru a wireless Honeywell was reserving the signal from thermostat- signal to AC-zone Climate Control was not there however. I was replaced the battery was replaced on the thermostat- which helped, there was a signal.

AC zone climate control - gave a signal to control board of the furnace, the furnace then gave a signal to 24B from 24B to the contactor. The contactor started with a rattle, the technician didn't like the sound of that right away. Everything was pointing towards the fact that the contactor needs to be changed, but technician decided to clean the contacts in the contactor instead. While the AC is running and the contactor is not working properly , the transformer was overheating - I wasn't able to keep my thumb on it which only meant one thing, that the temperature was above 120F. Since the cleaning of the contactor did help and it started up a lot better but still with a small rattle. Overall it was working just fine, the technician thanked them for choosing Sunny Appliance Repair and left to his next order.