To all of the home inspectors just starting out one of the most basic concepts to master in this business is the art of communication. A perfect example is to communicate to the parties on the selling side that mechanical items and access areas need to be cleared. Now, keep in mind by "asking" for this to be done doesn't mean that it will be done. Communicating is two parts-talking and listening. I believe a good communicator is more about being a better listener. If your request to have something done is not being met determine a better way to get this message across.
Perhaps reminding the owner upon your arrival before you actually get to these areas is all you need to do. By "politely" reminding them when you get at the home you will often get the results you need. Don't get yourself all worked up waiting untill you're at the point when that part of the inspection has arrived and you realize you can't get to where you need to go. This without a doubt can be frustrating. As a home inspector,don't let it get the best of you.