cracking on exterior brick wall
Masonry can crack for reasons other than foundation problems. Thermal and moisture movement is a common cause. When brickwork gets warm it expands, and when it cools at night it contracts. It may crack at this point, often at the frames which is a weak point in the wall.
When walls were built with lime mortar they could easily accommodate this movement, but with cement mortar cracking is more likely. Calcium silicate bricks are more prone to this than clay bricks. Nowadays we put in movement joints on any external brick wall which is longer than 12 metres.
If the crack is less than 5mm and equal in width it could well be thermal movement which is not serious, but it is worth keeping an eye on it. You can fix tell tales to the crack which monitor its progress over time and will tell you if the cracking is progressive.
Its a good idea to re-point it sometime as water may enter and cause further damage.
Is the house of solid brick construction, brick block cavity or timber frame with a brick veneer?