Repairing Oregon Scientific WGR800 anemometer

First, I'm aware of how hilarious it is that this is the first post in almost 10 years.  What can I say, my attention has been elsewhere directed.  And why am I posting this now, you ask?  Because I feel I have something to say which others may find of use.  I feel I should also add that I'm greatly tempted to delete most, if not all, of my previous posts ... I'm older now; I'll leave it at that.

Anyway, let's move on.

The Problem...

I maintain a small, basic weather station.  It's an Oregon Scientific WMR88 which is kinda the base model when it comes to weather stations that do more than tell you the time, temperature and barometric pressure.  This little setup collects wind and rain data in addition to the aforementioned basics and has done since 2012 when my better half bought it as a birthday present (clever cookie she is).  Now, almost 5 years on, the anemometer has stopped taking wind speed measurements and it turns out the bearing has gone kaput.

What to do?

Well, googling seems to show that most people either update/graduate to another system, or some might even track down a new sensor.  Neither of those options appealed to me firstly because I have a significant investment in time spent coding my own solution to read the messages this thing sends out and secondly because I'm looking at around $145 for a new sensor.

The Solution...kinda

Luckily, a single web site, in French no less, had the answer: http://www.station-meteo.com/forum/station-meteo-oregon-scientific/anemo-wgr800/.  What this site says, in a nutshell, is that a) the bearing can be changed and b) the bearing is of type 623ZZ.  What it doesn't say much of is how to go about changing it.  There was a single post stating that the "...bottom plug is mounted on grooves...".  All true but I aim to expand on that a little more.  Unfortunately, I didn't take my own advice and take photos of the operation so you'll have to wade through my descriptions and figure it out as you follow through the steps.  It's also probably a good idea to give this a full read through before you start to familiarise yourself with the steps involved and any "gotchas" I'll note. 

What You'll Need

Before we go any further, you'll obviously need to source that bearing.  Search ebay for "623ZZ" and you'll find plenty of options to suit your particular needs.  I bought 4 for a few spares (I'm wondering if the 'vane' bearing might also be getting close to end-of-life...) for $5 delivered.

As for tools, I used a small precision screw driver set (10pc in small black plastic case; you've seen them I'm sure) which can be had for about $5 from ebay.  Tweezers are handy, unless you've got the hands of a surgeon, and pliers.  My eyes aren't what they used to be so I also used a good strong light source and magnification for the fiddlier bits.  You might also want to grab a small container to put the parts in as you dismantle the unit to save you chasing a tiny screw around the floor.

Something else to bear in mind as you tackle this work, after some years in the elements, that plastic is likely to be brittle.  Should you get a little over zealous or let your frustration get the better of you, there's a distinct possibility of cracking the housing somewhere or perhaps even breaking off one of the anemometer cups which, needless to say, pretty much means you can pack up and trash the whole thing.  The fact that you're reading this means I made it through safely...but I reckon it was a damn close call.

Ok, let's get down to it.

Disassembly

Start by unscrewing the spinning hub from the body of the sensor unit, the same as you would to replace the batteries.  Inside, you'll find a pretty basic setup with a 'mast' topped by a black 'donut-y' thing secured with small 'C' clip and a couple of small philips-head screws holding down a white bracket (sorry to have to use technical terms).  That mast spins with the anemometer cups and you'll see the bearing that's caused the problem underneath that.

At this point, it's always a good idea to have a close look and take notes about what you're working on before you've taken anything apart.  Note things like the orientation of brackets and moving parts, the position of parts in relation to each other, etc, etc.  Write it down if you want.  Better yet, take photos (ahem...yes, well).  Sometimes even simple operations can go bad and having a reference for how things should fit can save a LOT of anxiety.

Now, using a small flat-head screwdriver, remove that c-clip, carefully!!!  Those things can fly off unexpectedly and, given its size, you'll never see it again and that'll be the end of your sensor.  With a small enough screwdriver placed into one of the gaps in the c-clip and twisting against the shaft (as you would to tighten a screw), you lever the clip from it's groove.  You'll see what I mean.  Just keep a finger against the clip as you guide it off to prevent it flying away.  Also, don't bend the clip because that'll also signal the end of your sensor since they don't work too well once deformed.  The black thing will now slide off easily and those 2 screws can come off too along with the bracket they hold down.  You'll now be looking at the shaft mounted in the bearing.  Feel free to take another photo.

That's the easy part done.  What comes next I'll describe as best I can but you'll need to gird thy loins because it could be frustrating.  If you turn the unit over with the anemometer cups stickup up, you'll notice a small plug in the center.  Underneath that is the other end of the shaft the bearing is mounted on and, as mentioned in that forum post linked to above, the plug you're looking at is VERY snuggly mounted on the grooves of the shaft; it might even be glued.  The aim is to remove that plug, allowing you to gently tap the shaft through the housing thus gaining access to the bearing, which simply slides off.  You might also notice that there's no obvious way to remove that plug, which is where the fun starts.  If you're better than me, you'll remove it without actually destroying it.  Alas, I was not up to that challenge and the plug for my unit is now history, basically having hacked the crap out of it.  If I had it to do over, I might try and use 2 small self-tapping screws (like the ones holding down that bracket perhaps?) on either side of the plug and use some pliers to pull the plug off.  I have a feeling that might work but you'll need those screws to have a good grip; it's a tight fit.  However you manage it, the plug is the hard part and after that, it's all very simple.  With the end of the shaft exposed, you gentle tap it through towards the inside of the housing.  Once through, as I said the bearing just slides on and off.  As far as I know, the bearings I got were symmetrical so I didn't pay any particular attention to which way I put the new bearing on.  You may want to confirm that with your bearings, just in case.

Reassembling

Similarly to how you removed the shaft from the housing, you'll need to gently tap the shaft, with the new bearing in place, into the housing from the other side.  I didn't notice any particular way to know how far to keep tapping except for how far the shaft stood up in the hole where the plug was.  Sound is usually a good guide but I was more worried about cracking the housing so I could have missed something.  Regardless, make sure the shaft goes all the way home.

Back inside the housing, you'll notice that the shaft has a flattened 'landing' close to the where the bearing sits.  That will match the internals of the magnet thingy (technical term there...) and you'll need to make sure that you feel them 'snick' together when you slide the magnet thing home, otherwise you'll never get the c-clip on.

Again, regarding that c-clip, you'll need to use caution.  Getting them on can be harder than taking them off so just be patient and take your time.  The general approach is to use a flat-head screwdriver, larger than the one you used to take it off and, with the clip in it's starting position, you simply push the clip home with the flat edge of the screwdriver.  Sounds simple but things can go wrong.  Firstly, getting the clip into the starting position can be fiddly because of the magnet underneath.  Here's where those tweezers really earn their keep.  If you don't already know it, that c-clip fits into a shallow groove on the shaft and trying to get that clip around the shaft anywhere but that groove just isn't going to work.  So, using those tweezers, place the clip so that the 2 ends are sitting in the groove.  Then, using the broad, flat side of the screwdriver, gently push the clip so it clicks into place.  As with removal, the risk of unauthorised flight is significant so you might want to try and block any escape routes as best as possible.  Secondly, the contact point between the clip and the screwdriver is, shall we say, limited so the natural tendency will be for the clip to slide on the face of the screwdriver.  As you can probably imagine, this is how clips get bent which, as I mentioned above, will generally render the clip useless.  The trick is to apply the required force directly towards the center of the shaft.  If you have the screwdriver face vertically angled at anything other than 90° relevant to the clip, you'll have problems.

You should now have a smoothly rotating, and thus operational, anemometer.  Congratulations!

Final Notes

On the assumption that the bottom plug was there to keep the shaft dry, blu-tack is covering the hole left by the trashed plug and I assume that's temporary.  I don't know if it's waterproof enough for the application and I really should check to make sure it's not hygroscopic.  If blu-tack isn't up to the job, I guess I could use duct-tape but I'll need to be careful not to upset the balance of the anemometer.

Considering how much I paid for the bearings, I find myself wondering how long the new one will last.  I have seen single bearings going for as much as $10 each.

Anyway, hope that helps someone.