Question
Hi Matt,

I just came out of the winter here in SoCal, and one of my rainbird sprinklers will humm but will not fully open the valve.  While it is humming I can back out the solenoid about a half turn and the valve opens, but now will not close when the power is removed.  I can manually open the valve, I can adjust the flow all the way down and remove the solenoid to verify good flow to it.  I think that the hardness of my water has a port plugged inside the solenoid, as I figure that they either create an electromagnet to activate the valve or they don't.  My question is can they be disassembled for cleaning or do you soak them in muriatic acid to dissolve the calcium?  I have 2 of these dirty solenoids because I saved the last one that had this problem, it was fixed when I installed a brandy new solenoid.

look forward to your response.
Thank you!

Powell  

Answer
Good diagnosis.
What I believe is happening is, the plunger inside the solenoid isn't lifting due to the calcium build-up. Most solenoids can be disassemble enough to get the plunger out and clean it. I think vinegar would be a safer cleaner though. There is a tiny spring behind the plunger and I'm afraid a strong acid might dissolve it.
Thanks for the question.

Matt