How do I change the bulb in the low beam headlight in my 2007 Mazda CX7?

Check the wiring on that light. Also check the bulb with a couple of wires to the battery, or swap the bulb left to right to make sure the new bulb is okay.

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This free video shows how to change a burnt out headlight on a 2009 Mazda 5 Sport 2.3L 4 Cyl.. Complete instructions for replacing a head light bulb on a 2009 ...

Low beam head light bulb replace 2000-2006 Mazda Mpv ...

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https://www.youtube.com/watch?v=kblzMLRJrok
Jun 29, 2013 - Uploaded by hp11208
Low beam head light bulb replace 2000-2006 Mazda Mpv .... My step dad and I successfully replaced a headlight yesterday! :-) ...I've lost it trying to replace the bulb. if anyone can let me know I would really appriciate it thanks ! ..... 5:00. Cleaning your IAC to fix rough idle on 2000 or 2001 Mazda MPV ...

there are a number of fueses for the headlights and a relay I believe , ck your low beam wiring see if you are getting 12 volts to the low beams if not find out why , maybe a break in the wires

1. I own a Protege and once the low beam bulb burns on one headlight the car electronics quickly cook the bulb on the other headlight as well. it is a poor design by the mfr. Pull both bulbs to make sure the low beam is not cooked.

First park your car on leveled ground, and it would be best if there is a white wall at a 10 feet distance from the car.
Once you pop open the hood, you will find adjustment screws at the back of the headlight. To locate them, look straight behind the headlight, and you will see two Philips head screws
The outwards screw that is close to the fender is for vertical adjustment, turning it clockwise raises the beam and vice versa
The inward screw is for the horizontal arrangement - counter-clockwise brings the light more towards the inside, and vice versa.
Inspect results while making adjustments so that you can narrow down to the right beam position.

Then the light has a leak and moisture is getting in.

Thanks for choosing FixYa and welcome. These new lights have two types lin one bulb, one for the low beam and one for the high beam. Find the bulb that isn't lighting for the low beam and replace it with a new bulb. If it doesn't work, you need to check the wiring to that specific light. Since it is only one, the new bulb should work.

check the ground connection of the bulbs. check the light switch. the headlight relay is located under the dash or under the hood.

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

For Low Beams: If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.

For High Beams (if separate from low beams): Aim the headlight directly at the line you marked on the wall.

Open the 2007 CX-7 Owners Manual (here is you don't have one http://www.mazdausa.com/MusaWeb/pdf/manuals/2007CX7OM.pdf)
Go to page 8-35 (P. 331 in the pdf). Close the hood, you're in the wrong place. Remove the cover in the front of the wheel arch to expose the headlight assembly.