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

Hi, I've just inherited my parents' house that has a T-Bird
irrigation system, which has worked very well for ~25 years (to the best of my
knowledge--I don't remember my folks ever saying it wasn't working properly).
The pump was changed 3 (?) years ago and continued to work fine but now that
I'm on the hook for everything, I've noticed that the pump rapidly cycles
(every 1 or 2 seconds) when it feeds 1 of the 6 zones. I have no idea when this
problem started but since it probably doesn't matter, I'll assume just
recently. My main problem is how to diagnose it.



The only thing I can think of that could cause a single-zone problem is
partially blocked heads, I've cleaned 6 of the 8 heads, which were heavily
blocked with junk from the river source (they may have never been cleaned), but
the pump still cycles although sometimes after running smoothly for 5 minutes.
Once when I turned it on, it started cycling immediately so I'm not convinced
I'm on the right track.



Any suggestions on how to diagnose this? I'll be cleaning the last two heads
tomorrow but I'm not hopeful.

Thanks!

Audios

Big thanks for the clean-the-valve suggestion. I'm embarrassed that I didn't think of that one!

So, I cleaned the rest of the heads (which were very plugged) and the valve (which was fine) but nothing worked so I decided to start from scratch and check everything again. It turns out I now had two zones that caused the pump to cycle constantly and a third (of six) that would sometimes run smoothly and other times cycle. I know only one cycled in the beginning so I assumed I was dealing with a random problem.

I called two companies to come look at the only thing in common, i.e. the pump, but neither one of them called me back. I guess they have too much work this summer to give a poop about customer service and any future calls from me! :-(

So, I decided to do what I could. There was nothing obvious at the pump by the river so I looked at what I could with nothing more than a screwdriver. I did notice the contacts on the pressure switch were very badly burnt so I replaced it and so far everything seems to be working fine! Yeah!!!

That said, I don't understand why burnt contacts would make the pump cycle. I can see it preventing the pump from running but such was not the case. It was more like the pump would come on and somehow cause too much pressure, then shut off, only to have some water get through through the heads, the pressure drop, and then the cycle would repeat. But how could the pump randomly cause too much pressure or, more likely, a pressure switch randomly think the pressure was too high and prematurely tell the pump to shut off??? It's a mystery to me.

It's also a mystery as to whether or not the burnt contacts caused the problem or a mechanical problem in the switch caused the contacts to burn as they repeatedly opened and closed.

If anyone can tell me, I'd really like to know for future reference.

Thanks,
Audios