For this job, I worked on a evaluation on this furnace system, as we arrived, furnace was not turning on. After completing a couple tests furnace turned on and was left running. Solder in furnace control board turned to be bad. Customer did not want to pay service fee because we have been out here many times, I explained to the customer that this issue could not have been figured out because last time system was already running perfectly fine and no issue were seen after all the tests were completed, she asked for the office to call her.