Tech found gas line turned off and inspected heat exchangers. Heat exchangers are very rusty but no holes. Tech explained that a dangerous crack could occur at any time. Tech also found open limit switch faults due to very corroded connections. Tech found only the first burner lighting due to corroded burners. Wires also corroded. Tech explained that he can get the unit going by replacing burners, but unit really needs to be replaced. Customer wants a sales appointment