If you know your model number, you should be able to find the manual online at Amana Instruction Manuals.
There is a link on the page if you need assistance finding your model number. An electronic (PDF) version of the manual may not be available for your model. Manuals that are not available to download can be purchased through the consumer affairs department by calling 800-843-0304.
If you are in the market to purchase a microwave oven, be sure to read How to Buy a Microwave Oven.
