CNR4 Desiccant Replacement

Tools

small blue handle channel locks
Small Campbell Scientific Phillips #2 screwdriver
Bubble Level
Stubby #2 Phillips Screwdriver
Optional but handy to have available tools in case of stripped screwheads
- tap and die plus appropriate drill bit (plus spares) for those screw combinations.
- cordless drill with charged battery
- a larger drill bit (1/4" or less) to remove stripped head.

Anti Corrosion Goo
CNR4 Desiccant cartridge
- Can purchase from Campbell Scientific or reuse one from crockpot.
For Optional fix:
- Small 8/32 or 10/32 or 6/32 or 4/32 machine screws, 1/2" or less in length.

Use small blue handle channel locks to loosen and remove the sensor cables.
Rotate CNR4 on its slender cross arm 180 degrees to it is upside down.
Use the small campbell scientific screwdriver to unscrew the small screws attached to the radiation shield. Place shield and screws on the ground
Use the screwdriver to remove the machine screws (carefully!! they are made of a very soft metal that will try to strip if you aren't careful)
place the screws on the radiation shield safely on the ground.
carefully pry open the CNR4 bottom plate. There is an o-ring that might try to pop off.
Inside the body of the sensors is a cylindrical white cartridge. Set it aside and replace it with a new / recently dried cartridge.
carefully put things back together. Dab the tip of each machine screw with the anti-corrosion goo before screwing it in gently.
once all screws are replaced, tighten them up again as if finishing lugnuts on a car wheel change.
Next, rotate the sensor back to operating position.
dab a bit more anti corrosion goo on the sensor cables and reconnect each.

If the screws strip out you'll obviously have a bit more work to do.
Stop what you're doing.
gently return any of the machine screws back into their original positions after dabbing with a bit of anti corrosion goo.
completely remove the sensor from the mounting arm.
Set on the ground / some clothing etc.
Now, the screw that is stripped, you'll need to drill the head off. Drill with the larger bit until the head is gone.
Change out to one of the drill bits paired with the tap and die. I leave it to you to select which combo. There are several because it is easy to break both the narrow diameter drill bits as well as the tap/die part.
carefully drill a deepish hole with this drill bit adjacent to the stripped head. You will need to go pretty deep here in order to get full thread use.
Use the tap and die to create threads.
do a bit of testing with one of the replacement screws that it fits comfortably and tightly into this hole.
Great, you're set. Now return to where you were and remove the machine screws and follow the original procedure above.

Once the sensor is back to original position finalize the level.
use a bubble level or horizontal torpedo level by placing it on top of the sensor.
there are seven separate screws at the tripod / tower end of the CNR4 cross arm. The four are used to keep the cross arm in a fixed spot. They form a rectangle.
Three of them are slightly larger and screw into a nylon material. Ignore the one closest to the sensor. It is the pivot and should be tight. The two screws with spring control the level. The middle right handles left-right leveling (rotational). The one closest to tripod/tower handles up/down. Adjust until the bubble looks good.