I just bought a lilliput 7" touchscreen. I plugged it in using the included cigarette lighter adapter, and the screen would not turn on.

After troubleshooting, I found that the voltage at the end of the cigarette lighter plug that connects to the screen is only 7V. This isn't normal, is it? I tried this in 2 cars, and measured the voltage coming out of the cigarette lighter itself (12V), so I'm assuming it has to do with this little in-line device that I believe normalizes the DC voltage to 12V.

Can I just use a straight-through adapter like any other car device uses (i.e. radar detector plug)?