Phone charger reading no amperage?
You probably blew out the fuse on your ammeter. An ideal ammeter has zero resistance, so when you measure current you need a load. 

Poorly made picture:



Notice the light-bulb providing a load. Try connecting a 100Ω resistor in series when you test, if you're getting 5V out you should get 50 mA. You can try lower resistances, but you'll want to ensure that the resistor you use has a high enough power rating. If you use a 100Ω I'd go with a 1/2 W resistor to be safe. If you only have 1/4 watts lying around then try a larger value resistor.