Belt Tension  

The belt tension figure is a measure of the resistance felt by the stepper when moving the axis. On a correctly set up machine this does equate, roughly, to belt tension.

But other things can affect mechanical resistance.

First, with the power off, move the axis by hand; is it smooth? Does the resistance stay the same over the whole range?

Clean and lubricate the smooth rods, check they are not damaged/scratched. Check the idler pulley is not clogged, out of line, or damaged (loosen the belt and try turning it with your fingertip, is it smooth?)

With the belt loose try turning the stepper motor by hand; is it smooth?

Retighten the belt until it just begins to make a low musical note when plucked...

Make your next print this:

https://www.prusaprinters.org/prints/46639-tension-meter-for-the-gt2-belts-of-i3-mk3s-or-prus

It MUST be printed in Prusament PETG or the spring tension will be wrong.

Let us know how you get on.

Cheerio,

RE: Belt Tension

That indicator is great. FYI you don't absolutely need to use Prusa PETG. I used 2 other brands of PETG along with Prusa PETG and they ALL read the same.

RE: Belt Tension

FWIW, I printed two of these and get two different readings.  Same filament and printer.  Just different settings for flow rate after calibration.  I check with both and make sure that they are both under the reading.