[A/S] 12-volt outlet in truck

[<airstream720@xxxxxxx>]

We like to travel with our laptop in operation.  I use a 12-volt inverter and 
am now on my 4th one.  The laptop is rated at 90 watts output and the 
inverter is rated at 200.  However, when plugged in it either overloads or blows a 
fuse in the truck.  (I'm sure there are more technical terms for what I am 
trying to say).

I am assuming that the outlet in the truck is faulty.  When checking the 
power options on the computer while plugged in, it keeps flipping back and forth 
between AC power and battery power.  When plugged into a 12-volt outlet inside 
the trailer it shows constant AC power.  

How do you check these cigarette lighter thingies (to use one of Hunter's 
terms) to see if they're OK?

We do have two outlets in the truck, but the other one (which is 'on' all the 
time) is used for the SmartTire.

Thanks,
Verna