This is a question that should be easy to answer but I cant find an answer anywhere. Using my 70D in manual mode when I adjust the shutter speed and f stop, the mark below the meter should move. It doesn't. No matter what I do it remains on -3. auto exposure/AEB is turned off. Am I missing somehing or what?
Oh trust us... we HAVE to ask those really basic questions. If we don't... there will, inevitably, be the day when someone misses something incredibly basic and we spend days trying to help them.
I do actually know someone who had a problem with a computer mouse that would not work... this person was not very technical and didn't know what makes a computer mouse work. It turns out they had placed the mouse on the table... upside-down. We spent hours and hours trying to help them (over the phone) because nobody thought to ask the question as to whether the mouse was actually sitting on the table right-side up (it would practically be an insult to ask someone such a question, right... turns out... not necessarily so!) We hope you understand.
As for that electrinic needle you see... it will ONLY start moving if you come within 3 "stops" of what the meter suggests as a proper exposure and you could easily be off by many many more stops than that.
As you mentioned you are in "...broad daylight. In Arizona." I'll ask you to dial in a very specific exposure.
Please set your ISO to ISO 100
Please dial your f-stop (Aperture) to f/16.
Please dial your shutter speed to 1/100th (although you *might* need to bump it up slightly).
This assumes you are outside during a sunny day pointing the camera at an object which is neither white nor black and you are pointing the camera to an object in full-sun... not hiding in shadows.
This is the "Sunny 16" exposure (it turns out the Sun provides an extremely consistent and reliable level of light at mid-day.)
Now when you look through your camera, the needle should be pointing either to the "0" indicator in the middle of the scale ... or a value reasonably close to it (within one stop). Also... as you adjust either the aperture or shutter speed while looking through the camera, you should see the needle move (assuming you "wake up" the metering system usually with a half-press of the shutter button.)
You probably aren't messing with the exposure lock feature... but "just in case"... avoid pressing the exposure lock button (the asterisk button on the back of the camera.) That button is designed to allow you to point the camera and meter the light on something... then "lock" the exposure and re-compose to point at something else WITHOUT allowing the camera to re-meter the exposure. (It clears this lock automatically either after you take a shot or after not touching anything for about 5 seconds or so. Tapping the AF point selection button on the camera will force it to release the lock immediately.)
If you are in P mode does the camera function and expose properly?
If you switch to M and select the same Av and Tv that the camera selected in P does it still read --3?
Did you try removing and reinstalling the battery?