I've got an in-ground pool, and a DE filter from Jandy. The pressure gauge is in an assembly bolted to the top. The assembly looks like something like this (image from catalog, mine is pretty much identical):
Today, when I powered the system down, the pressure reading didn't change. I pulled the gauge assembly off and tried blowing it out, removing the relief valve, etc, etc, to no avail. I have to assume something has gotten stuck in the gauge inlet.
Is there any good way to fix this? At the moment I can't even figure out how to get the thing apart.
The ring on the front (where clean/dirty are written) does rotate, and if I have no other answer, I'm going to try prying that off and see where it leads me.
UPDATED: @mikes had the right answer - swap the thing out. I ended up swapping out the whole unit, as I had no idea how to (non-destructively) get it apart. Someone else might like to know how to disassemble the thing in order to get at the actual pressure gauge itself:
Remove the trim ring. I found a notch on the bottom and pried with a screwdriver
Unscrew the pressure gauge. It's normally threaded, however whatever they used as a sealant didn't want to let go for me. Excessive force may be required. Because I wasn't sure of what I was looking at, and thought perhaps it was formed in place somehow, I ended up cutting the thing in half to find out.
Thus, we can see that as long as you can manage to get enough force on it to unscrew the pressure gauge, it should be possible to replace JUST the gauge portion, instead of the entire unit as I have done.