Trying to help my veteran father-in-law. The blower fan won't shut off unless you push the door switch. Blows cold air only, noticed sparks in what looks like a relay of sorts on the circuit board. Gas valve looks like it was recently replaced. Recently told it could be a high limit switch. Want to replace circuit board, but should I replace the Hi-Limit switch also. He lives 40 miles away, and I would like to help him out in just one trip. Any Ideas? I have found the parts online and will pay for them but would be thankful for any suggestions.