[12V Car outlet]

So you mean I can't hook up with a regular led and resistor to the 12V outlet (too much current), right?!  Then I will use a 9V battery to light up the led. 
Just for curiosity, my last question was that if I cover up the display on the power supply, can you measure how much maximum current from the power supply?  For example, I didn't know how much current from the 12V outlet, can I measure it?

[12V Car outlet]

Hi guys, I would like to know how much maximum current is there normally coming from a 12V car outlet, because I want to connect a resistor and LED with a car charger adapter.  By the way, how can we measure the maximum current from a power supply if we don't know the current limit?  Thank you.

Honford