I'm hoping to confirm what a person told me is causing a brake related noise before doing the repair, and I'll try to keep this short as possible. I have an '06 GMC Sierra extended cab, 1/2 ton, 2 wheel drive,with only 13,000 miles on it. And I'm a contractor, and a couple weeks ago, I was coming back from a job that was a ways up a mountain road, and coming back down this road is not the best on brakes, especially when a truck as high geared as mine isn't easy to slow down by downshifting. Anyway, I've been on roads like this here and there, so I'm sure my brakes have been getting glazed over time. I get to the bottom of this hill and I'm getting a high pitched squealing noise that I know is glazed brakes. That wasn't a big concern, but I noticed when I got on flat ground I was getting a "chirp" that was keeping with the revolution of the wheels while driving, no braked being applied. I confirmed it's coming from the left front wheel. It's the same pitch as the glazed brake sound, but like a said, more of a "chirp". I get home and figure I'll see what happens the next day. In the morning, it won't do it all.....all the way up to this job.....no unusual noise, but I'm also not braking nearly the same way. Anyway, coming home, same thing......squealing brakes, and the chirp is back on flat ground. To fast forward, I end uo going to my mechanic, and ask him what the chirping when I'm driving is coming from. He says it could be a lot of things, but he'll check it out if I want. He takes the front brakes apart, scuffs the rotors, scuffs the pads(which were glazed good), makes sure everythiing is as it should be, adjusts the back brakes, and puts it all back together.He even commented that the pads looked like they had got pretty darn hot, and the rotors had a nice mirror like finish. My squealing brakes are gone, but after I drive a bit and apply the brakes a few times, and not necessarily going downhill, the chirp is still there. I had to go to another out of town job the other day, and go over a different mountain with not nearly the downhill slope, but you still have to brake a fair amount. Anyway at the bottom, I turn onto a highway, and taking off from a stop, there is the chirp, and it speeds up as the truck speeds up, but I noticed it goes away if you keep driving, and don't apply the brakes. Further experimentation proves that this happens after you have braked at least few times, so it is definitely related to the brakes/rotors warming up, and does go away if allowed to cool off a bit before braking. Now, my mechanic says the next step would be to turn the rotors and put new pads on, and that maybe the rotor is just not perfectly true, and is just barely getting touched by the pad as the wheel turns. Let me also add that there is no pulsating brake pedal, indicating a warped rotor, so that isn't it. Anyway, his estimate to turn the 2 rotors and put new pads on was a little pricey, and I'm considering doing it myself, so when I called to get a price on the pads and started to describe the problem just like I did here, the guy kind of stopped me and said(with confidence) that what was happening is that I have hard spots on the rotors from them getting hot(which they have), and that those hard spots will "bulge" out, if you will when the rotor gets warm/hot from braking, and can just barely come in contact with the pads while driving, and make this high pitched "chirp". This makes a lot of sense, and he told me this like he's seen this before, and it also explians why if you drive a bit without braking, or let the truck sit, the chirp is gone......until you brake a few times or so. So my question is; does this sound like the cause of the chirping noise to anyone? He also said you could probably turn the rotors, but the hard spots are still there and the noise could come back, or not. It's a hit and miss. Sorry for the long story, but I wanted to be thorough, and if you made it this far, thanks for reading, and really appreciate any feedback. Thanks in advance!

The problem with this system is not being able to adjust the temperature of the heat. The temperature control knob can be on full cold, and you will still get full heat. I do get A/C with the system set on MAX A/C, however, and with it set on NORM A/C, I get heat instead of A/C. The control panel has been replaced, and I have also checked for any vacuum leaks. I was told that possibly the air flow door on the heater box assembly may be broke. Has anyone had this problem with their Explorer? Thanks.