TODAY | November 20, 2013
>>> back at 7:40 and this morning on rossen reports, a hidden camera investigation before you hit the road for thanksgiving. today national investigative corr correspondence jeff rossen tells us.
>> that warning light pops on your dashboard. it's completely natural. the fix is easy. just add some air but would repair shops do the right thing? this morning, our hidden cameras are rolling and what we found has never happened to us before.
>> sir, jeff rossen from nbc news. i want to talk to you about a customer that came in a couple of weeks ago. just wait until you see what his repair shop did and this mechanic astonished us.
>> reporter: we set up a scenario with this 2010 chrysler minivan and hired this certified mechanic to inspect it along with the tires.
>> the car is in perfect condition. it needs nothing.
>> reporter: then we had her rig a simple problem.
>> we're going to let air out of the tires. trigger the dashboard light to come on.
>> this is a common situation because this time of year when the temperature drops tire pressure drops.
>> that's it.
>> what's the fix for this van.
>> the fix is free air .
>> that's it?
>> reporter: we wired the van with five hidden cameras underneath, inside the side view mirror and even behind the tire capturing every angle.
>> how are you? i had an 8:30 appointment.
>> reporter: then we sent this female producer to six shops around new jersey. from car dealers to national chains to independent garage with that warning light on.
>> i have this light that came on in my car. i'm not sure what it is.
>> reporter: things start off promising at these two chrysler dealers.
>> in the cold and the heat the tire pressures change. all you have to do is go and put air in it and that's it.
>> that's all you need to fix it?
>> that's it.
>> reporter: the dealers don't charge us anything but will we will as lucky at the chain stores ?
>> you don't need to fix it.
>> reporter: it gets even better at this firestone. this shop even taking off our tire to inspect for leaks. so honest.
>> i don't need to fix anything?
>> no, just keep an eye on it.
>> reporter: and it's all free. jeff rossen from nbc news. we were wondering if you were going to charge. you sent her along for free.
>> yeah but she will come back. you have to trust your auto mechanic like you have to trust your doctor. you to go somewhere where you can trust the person.
>> reporter: but what happens next at this independent shop truly surprised us.
>> if you could just tell me what i need to do to fix the car.
>> reporter: our producer tells them she is clueless making her an easy target.
>> i don't know anything about cars.
>> don't tell the mechanic you don't know anything. we are not like that so i give you the tip.
>> reporter: that's right. he just gave our producer free advice to avoid getting scammed and diagnosed our problem correctly.
>> you don't need tires. we can change it. we make money. but if you don't need it, you don't need it.
>> jeff rossen from nbc news. you told her not to call herself clueless.
>> that's what i do.
>> why did you go above and beyond to help her so much.
>> that's how i was brought up.
>> thank you for being a good guy.
>> you're welcome.
>> thank you very much.
>> thank you.
>> in the end, every single repair shop did the right thing. a rossen reports first. even our expert was stunned.
>> to see that they were really trying to give great service helping out someone that really didn't know was wonderful.
>> so what if this happens to you? you wake up one morning and your tire pressure warning light is on? you can fix it yourself. we posted a very simple how to video on our website right now. today.com. takes just a few minutes. savannah, anyone can do it. even you, even me.