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5 zone system. Zone 1 is not coming on full but is instead pulsating with weak water flow. I replaced the solenoid but this did not help. I changed the wiring from zone 1 to unused zone 6 at the controller. This also did not help. The clerk at the hardware store didn't think the diaphragm would cause this. No leaks and this zone was working a few weeks ago. Any ideas?

Quoted from "Phxflyer"

5 zone system. Zone 1 is not coming on full but is instead pulsating with weak water flow. I replaced the solenoid but this did not help. I changed the wiring from zone 1 to unused zone 6 at the controller. This also did not help. The clerk at the hardware store didn't think the diaphragm would cause this. No leaks and this zone was working a few weeks ago. The zone operates with good water flow if I open the valve manually.

It's an Irritrol 205 series valve. I should have picked up the diaphragm but the guy had me convinced it was the controller with this kind of problem. It was a counterman at SprinklerWorld. He seemed so sure, but swapping out zone 1 with unused zone 6 didn't fix it so my next guess was the diaphragm.

I'll post here tomorrow if that fixes it so it could help others.

That did it! It was the diaphragm. Your advice of attaching the new diaphragm in the bonnet first made the assembly a piece of cake. I just put one screw through a little on each side, lined it up over the bottom, continued to tighten those two screws, then put the additional 6 screws in. No leaks and it worked immediately.

Upon questioning the clerk at SprinklerWorld again about it being the controller, he said some Rainbird controllers are known to have a problem that causes a pulsating chatter. I have a Champion unit. And I think what I called "pulsating" was just a very weak flow causing the heads to momentarily come up then drop repeatedly.

In any case, again, thanks for your words of wisdom.