Since they are only 4 years old i m guessing they were replacements so maybe the wrong ones were installed not all turbines work with all roof pitches or these just haven t been leveled correctly.
Roof turbine vents not spinning.
A turbine may fail to spin if the bearings become rusty or.
The popular ridge and soffit ventilation systems and the traditional metal pot vents are also passive ventilation systems.
You can usually adjust the level by turning the turbine body.
Examine the turbine from the exterior from the roof.
A turbine vents spins with the slightest breeze.
I ambled around the roof shooting wd 40 specialist spray stay gel lubricant into all the vents getting them spinning smooth and easy.
The faster it spins the more air it exhausts.
If they spin freely but just sit there when on your roof i d say they aren t level.
Climb up into your attic and look at the vents from the inside.
In fact when i was headed to the last vent i noticed the the others were spinning on their own quietly with only the slightest hint of wind wafting by.
As soon as it starts to spin it vacuums air out of your attic.
My attic turbines are not turning step 1.
This is a bad thing because it blocks the air flow.
It s not uncommon for insulation to have been jammed tight out to the edge of the roof.
Inspect your turbine vent and make sure the top spinning portion is securely anchored to the standpipe using sheet metal screws.