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Question: does it get any power from the car adaptor to power the backlight?  and how bright is the backlight?
Document: also the unit uses a small watch battery to power the unit without the backlight. would be nice to have maybe a AAA or something more standard (just a thought)...... this unit did however work well on my motocycle 8)
Put it in the pocket below my head unit in my car. Works great! Nice and bright but not too bright. Temp is ~10-15 High. Can't really beat it for the price!
I install it on my 96 Ford F150 XLT and connected it to the ashtray light that turns on when I turn on the truck's light! It is precise but if you park the car under a bright sunny day on summer, it will take time to adjust to the internal and external temperatures as the internal temperature of a closed car on this condition gets quite high.
You get what you pay for. This device cost me less than $20 and I was a little optimistic when it came to its temperature reading when buying. I was thinking maybe this was one of the good ones. IT IS NOT. I tested it over a period of a month. It is always off by at least 10 Degress Fahrenheit. I will just use it as a clock in my car.
I ordered this meter to be used as an RV refrigerator monitor. The clock, and volt meter seem to work OK, but the thermometer was exceptionally accurate. The "outdoor" pickup reacts quickly, but the case temperature slows down the reaction of the "inside" reading. I am going to order another to see if I can get it to work in the Car which doesn't have a thermometer.
It always agrees with what other people's car read within a degree or two. Sometimes the internal temperature readings may get skewed because it sits really close to the AC vent, but who cares? You know how hot or cold it is inside the car. Outside the car is what you want to know and it does a pretty good job.Took about an hour and a half to install.
The best part about the thing is the clock - it's easy to program and has a really bright LCD display. In full sun in the surf of the beach or a dark campsite at night, you can see the readings clearly no matter what.
It's a great product, but for my 4Runner I want the outside probe near the from bumper. I had a brand X that had plenty of cable on the sensor. For this one, I had to splice in  additional cable. Fortunately that does not seem to affect the accuracy of the readings.Other than that, the display is  bright and easy to read.
Good accuracy. Displays 1/10ths of a degree which allows monitoring of trends, such as just above freezing and dropping or rising. Also displays time and temperatures in its internal battery, so available at all times, not just when receiving 12v power. Very easy to switch display colors with external  switch. Cables for sensor and power are attached to the right hand side of the display, making them more visible if mounted on the left hand side of a dashboard.
We thought this was just what we needed, however it came in a plain box no instructions. That would be ok if somewhere it told us the battery size. Had to open several packages and spend over $11 to get watch batteries (2) to run it. Not very happy.
Answer: It does get power from the adapter which gives you the voltage reading and powers the backlight. The backlight is pretty bright.