grammar dikduk - Is a vav before a verb in the Chumash always a tense changer?

I know that the vav before a noun can be a vav hachibur (cf http://www.torahmusings.com/2012/12/on-the-prefix-vav/) but in front of a verb it changes tense (past to future and vice versa) and may or may not also include the idea of "and".

But is that tense hipuch inevitably the case? Is understanding of the chumash text driven by this tense change as an absolute rule or is its application selective and controlled by some other understanding which contextualizes (either grammatically or logically) the verb and demands that the vav operate as a vav hahipuch?