How do you test a belt tensioner?

[Jerryl]

Will be looking at one just to have as a spare . . . . Besides the obvious bearing . . . How can you tell if a bent tensioner is bad, i.e. “weak spring”. How much for a used belt tensioner?

 

[charlief1]

Not sure on the GN one but on the newer ones they usually have a mark on both sides. When the marks line up it's bad.

 

[Heg87t]

Not sure on the GN one but on the newer ones they usually have a mark on both sides. When the marks line up it's bad.

Ours has an triangle on the one side and a rectangular window on the other side. if the triangle is outside the rectangle the tensioner is weak or the belt is too long.

 

[Jerryl]

Ours has an triangle on the one side and a rectangular window on the other side. if the triangle is outside the rectangle the tensioner is weak or the belt is too long.

Is there a way to inspect it when it is off the car?