My garmin 530 grade is not working properly. It is showing negative grade going uphill and not showing the actual grades.. most of the time it is 0% grade

to my understanding gradient is being calculated by altimeter data collected over a certain distance (20m?) , meaning that there is smoothing and incorrect readings when real gradient is changing significantly within the required distance where calculation takes place.
Does anybody has a better explanation on how gradient is calculated?

Test the Sensible Grade from the Garmin IQ store, in the settings it have few levels of accuracy:
apps.garmin.com/.../dab102f5-7172-49e4-9b46-b726a760e2ac

For the wet altimeter problem, my solution is simply to take the 530 off its mount and give it a few taps on the handlebars.  The altitude reading will then correct over the next few minutes (and make you look like a climbing god)

did not work for my 830 ((

I am also the gradient change very slowly compared to my Edge 520, which unfortunately had the battery fail. It seems to be common.

I experience the same on my Edge 530 for the last few weeks. Readings are completely wrong. The problem coincided with the latest software update.

I have same problem with my edge 530, i notice it will only arise on wet rides, or when sweat fall on my edge 530. I soaked my edge overnyt it went back to normal... i guess water or moisture is able to penetrate in the altimeter sensor holes. I will try to use silicon cover next time maybe it can protect the holes from water or moisture from going inside.

Hi Lupo, I read your post and I wanted to know what else did you do to fix the problem about the barometric altimeter.  In my case, the grade was showing me wrong and the altimeter was not working properly.  I have de same edge 530.   Thanks