If the charger has a fault, you will have to send it back anyway. Try connecting it and plugging it in. Make sure you have the polarity right of course. If the battery is being short circuited, it will cook the charger. If not, it should behave normally and you can use that multi-meter in its volts mode to see what is happening at the battery terminals. Anything between 12 and 14.4 volts is "normal".