A corrosion-resistant, solar powered piston extends to open and close greenhouse vents automatically. Piston wax expands and contracts adjusting the vent as temperatures change. Most openers support up to 15 lbs. (Below is a general sample instruction for the thermofor solar vent opener - this example not be an exact match with your current vent opener).

ADJUSTMENT (REF)

After allowing the solar vent opener  unit to reach the temperature at which you require the window to start opening hold the window slightly open and firmly turn the adjusting screw see fig. 4, in the direction of the LO arrow (clockwise) until the unit begins to support the window without assistance. Any rise in greenhouse temperature will now cause the window to open wider. Further adjustment may be necessary in which case repeat the process being sure to take the weight off the unit, by hand, as before. Turning the adjusting screw in the direction of the LO arrow (clockwise) starts the window opening at a lower temperature. Turning the adjusting screw in the direction of the HI arrow (anti-clockwise) starts the window opening at a higher temperature.

PLEASE NOTE: ADJUSTMENT CANNOT BE MADE WITH THE WEIGHT OF THE WINDOW ACTING ON THE UNIT.
As the cylinder is positioned to allow it also to sense the cooling effects of any chilling air from outside the unit will automatically react and adjust the window accordingly for added protection to your plants.

Will open window up to 37-1/2 cm (15")
Opening temperature can be set between 15 deg C to 25 deg C (59 deg F to 77 deg F)
Will lift up to 7kg (15lbs)