Arrived on site to diagnose a (2) 2000 year old system. Upstairs was not cooling or operating. Downstairs is not heating. Spoke with clients they advised heating has not been working since winter. Thermostat upstairs is not working and client can’t get set temperature to go up or down. Inspected upstairs unit. System would not turn on. Checked out connection, voltage and main circuit board. Eliminated thermostat and jumped system and system turn on. Cycled in heating and cooling. Both temp split and rise are good on upstairs unit. Recommend replacing thermostat to get system operating. Inspected downstairs unit. Heating mode would produce hot air. Checked for voltage, connections, Continuity, all good. Sequence of operation will start up till it got to gas value and not flames is created. Checked gas pressure on supply line and gas vale on manifold gas pressure. Was getting gas pressure on supply but valve would not open up. Cycled a few time and showed a gas pressure spike for a co