I had not thought of that problem.
But now that I have, I would use an air cylinder and an external spring to keep it closed. Sounds a lot less complicated than a motor. Unless you don't have air on your truck...

I may do that if I run in to space problems when I install my AC.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-