The question is how I fix this

I appreciate our children, but they aren’t always the smartest people in the world.  All of our kids have undoubtedly wonderful jobs, they own their own homes, and they are kind and loving people.  They are also actually smart when it comes to their jobs. When it comes to normal life, and having some proper sense, they are sporadically lacking.  My son is a truck driver, and he owns his own truck. It took him a couple of mornings to realize that there was something wrong with his Heating and A/C system.  He had been driving for about a hundred miles, when he realized that it was getting undoubtedly tepid in the cab. He turned on the air conditioner, but nothing happened.  He tried to adjust the temperature control, however he couldn’t get the temperature control setting to even show. He had the outside temperature showing, but that was it. He called and he asked to talk to dad.  I provided our hubby the PC, and I told him who it was. All our hubby could ask was what was wrong with the truck. When our son told him about the Heating and A/C, our hubby asked him if it was on. I know that got our son upset, however he once again asked if it was on.  Our son started to push buttons, and quickly we heard him say, ‘UH-OH’ . That was all it took and we both began to laugh. He hadn’t flipped the switch to go from heating to air conditioner. He laughed and he said he knew he had forgotten it, however he just wanted to talk to dad.

HVAC service plan