Received a call that the first floor furnace was not operating, upon arrival I found that the furnace was flashing a code 4 which is an open limit. I checked all the switches electrically and confirmed that they are all closed as they should be, upon further diagnostics I removed the plug from the board and found that the pin connections are loose. The board and wire harness should be replaced to make sure that the furnace doesn't trip on a false error in the future.
