Arrived onsite for maintenance for one gas fired boiler. Requested the customer turn on the thermostats up to heat and confirm operation of the boiler and each zone valve. Turned the boiler off and removed and cleaned all burners and wiped cleaner the burner compartment. Performed a visual inspection of all electrical and inspected all external water components such as the exp tank, fill valve, backflow preventer and the circulator pump. Found the pressure relief valve in horizontal position; recommend replacing. Found fault in pressure temperature gauge; recommend replacing. System working but recommend upgrading due to age and condition.