Ventilation problems-gable and ridge vent, no soffit

Hi, I own a colonial style house built in 1970 in new england. Our house has gable vents and a ridge vent, but no soffit vents. Part of the 2nd floor ceiling attaches to the bottom of the roof rafters so there is no clear air flow path to create a soffit vent (short of tearing the roof and sheathing completely off). My house orientation is east/west so I generally get good cross ventilation. This winter I discovered there was quite a bit of moisture in the attic. This spring/summer I was planning on installing a powered gable vent fan on the east side of the house to help pull air through. The question I am wondering is should I seal up the ridge vent or keep it? Sealing it up would create one entrance and one exit for the fan. Keeping it open would allow more air to escape the attic.

Any information is welcome!

Tricky question.
I would install the fan first and see what a years results were before i considered closing off the ridge venting.

Also, as others will jump
In to
Tell you, it is possible to put vents at the bottom of your roof to substitute soffit venting.

I’d try your thoughts first.

thanks! Good Idea about taking incremental steps. I’ve heard about the roof venting, but am even more nervous about those. The roof pitch is not very steep and am afraid of snow/ice backing up through the vents.

Use smart vent after you fix the air leak.

Increasing the attic ventilation is not always the right solution because it would allow more air to escape, pulling in additional warm, moist air from the living areas. The real solution is to seal off your attic access points, install adequate levels of insulation, and plug ALL air leaks.