The rain gauge hardware out on the garage roof feeding info to my home automation system is pretty old. It’s been in service I dunno – six years?, and on a shelf waiting to be installed for maybe 10 years before that. It stopped working a few days ago.
It’s not a low-maintenance device, and fails a couple times a year. Usually the small funnel tube from the big collector to the bucket counter inside clogs up. (There are now 4 layers of screening above it, and it clogs much less often.) So I (hauled out a short ladder, climbed up,) took it apart and looked at the tube: Completely clean.
OK, as long as it was open, I flopped the tipping-bucket mechanism a few times by hand. Seemed to move OK, so I put it all back together. When I got in the house and looked at the Pogoplug that logs everything, I could see a couple of new counts from those manual flops. Fine.
It rained some more, but it still didn’t register. I opened it up again and looked more closely for binding, etc. Looked good. I flopped it a couple more times by hand and put it back together. The Pogo noticed those flops. But just to be sure water would actually tip the buckets, I went out and slowly poured about 50ml of water into it. With its 8.7″ diam collector, that should be around 0.05″ – or 5 counts. I could clearly hear the bucket flop about that many times. But the Pogo didn’t see it. WTH?
The next time I took it apart I almost gave up until I touched the metal contact coming out of the end of the reed switch – and it moved! The glass reed switch was broken. Rats. But at least now there’s hope.
I cut the soldered-on wires, took it all apart and brought the guts inside. After (cleaning it up and) pulling the reed switch, it looked like this. Fortunately, the reed switch drawer had an almost identical switch (but not broken 🙂 ).
When I tried to remove one of the rubber grommets that held the switch, it just crumbled. Not surprising. I found another bit of rubber 
that just fit the new switch and made a grommet out of it. The one remaining (old, hard) grommet was slightly bigger than the switch tube, so I wedged a bit of card stock in for a better fit. Picture was before pushing the switch fully into place. Crude, but should last several more years.
Adjustment was touchy. Fortunately, the nylon screws/locknuts let me move the bucket and attached magnet to just the right distance from the reed switch for what seemed like reliable operation.
Put it all back together, took it back apart to put in the parts I missed, and put it all back together. I’d soldered some pigtails on the reed switch, and tied them to the original wires with very small wire nuts. Maybe some time when the weather’s nice I’ll solder them, but they should be OK for now.
For a final test, (after taking the bottle with a hole in the bottom down, loosening the cap, and holding it up again) I drizzled water slowly into the collector and listened for a couple of bucket flops. Back in the house, the Pogo saw them! I think it’s fixed.