DIY Heating plus Air Conditioning cleaning breaks system

I was learning online how your Heating plus Air Conditioning system should be cleaned out plus maintained once or twice a year.

I am kind of handy with a tool belt so I decided I should just do it myself.

I watched lots of videos plus learn up on everything. Then I got to toil with my tools, a vacuum plus some oil. I took my time plus was absolutely careful however when I put everything back together, my Heating plus Air Conditioning system simply would not turn on. I took it apart again plus looked at all of the linkion however everything was right. I knew I had to call in the professionals. This was over my head. A real Heating plus Air Conditioning supplier came out the absolutely next afternoon plus the contractor took one look at my Heating plus Air Conditioning system, flipped a switch on the side, plus said, “well here is your problem.” I felt so stupid. I had simply turned off my Heating plus Air Conditioning system like you might turn off a light switch. The switch must have gotten bumped when I was moving things around. It might have even gotten caught on the cleaning rag or something. I did not even know there was an off switch! Other than that, the contractor said I did a good job cleaning, for the most part. He offered me some hints plus tips for next time however he also indicated that his supplier cleans Heating plus Air Conditioning systems for absolutely little money. It sounded like a good deal however I kind of just want to do it myself. How else will I ever learn?