SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

No reason you can't replace the Maxipaws. With high pressures at the heads you can use PGPs or other rotors. It can be something as simple as a grain of sand in the wrong place, as to why the 'trip mechanism' fails on those impact heads.

Boots is right. Sometimes it's simple. Half the time I'll find a twig or part of a bush growing in there. Then you have other reasons. Sometimes there's a part broken or missing. It could be a pressure problem. Maybe a leak in a pipe you're unaware of. Sometimes they just stop turning and only God knows why. Sometimes putting in a new one makes everyone happy. You can just unscrew the guts and switch them out if digging it up is a problem. I've seen those cemented in a patio. I clean out the cannister with a garden hose before taking the guts out.

I just want to add that you don't want rotors and impacts running on the same zone. Either go all impacts or all rotors. Here's a link that will give you more info than you want to know. It might help you though. Good luck!

http://www.rainbird.com/pdf/turf/Impact_Guide.pdf