Wow, has this become a "hot" thread..... How shocking.
Fact is that AH systems have changed over the years, so to truly understand the details about any particular model, it's important to research yourself.
Look at the unit you have and write down the exact model number. From there, download and save the user manual for your exact model from the AH Web site. READ AND LEARN from the manual.
Also, as many have suggested, Roger Berke's web site provides a wealth of tips and information! Register on his site and use it. He's also a valuable resource for parts and advise on service technicians in whatever area you are located in.
To someone who has never had an AH before, it can seem to be a daunting system. However, once you spend some time educating yourself, as well as actually living with it, you'll come to love it!