AC adapter polarity

FNG here. I hope I'm in the right forum. I just bought a sirius satellite receiver with a car kit that uses the cigarette lighter as a power source.   I am too cheap right now to buy the home kit, so I just bought a universal AC adapter(12V) with the intent of using it at work also. The adapter has the option of changing polarity from + to -, but I'm not sure what polarity my receiver uses. There are no markings in the manual or on the device itself or on the power source cord. Is there a way to test this before I plug it in? Is there a standard that most of these units use? Any help will be greatly appreciated. Thanks, Chris

The standard is negative ground. Use a volt/ohm meter to check your adaptor is set correctly before you plug it in. The center pin of the male end of the cigarette lighter plug is the positive and the outer contacts are ground or negative. Make sure it's right first, because if it's backwards the radio won't survive.sparky

Thanks! I took both adapters to Radio Shack and had them test My cheapo plug in adapter agaist my cigarette lighter adapter with a voltmeter. The cigarette adapter measured +13.77 and the plugin measured +17.34. It worked fine for a few minutes, then started cutting out. I unplugged it immediately and the unit felt kind of warm. I'm afraid to use it anymore. The plus side to my tinkering is that I found that if I just turn it on in my truck, it will transmit far enough to reach every radio in my house. That'll get me by until I buy the correct equipment. Another example of the idea that cheaping out doesn't pay