CR6 maintenance
Protect the data logger from humidity and moisture. The data logger is designed to operate over a wide range of temperature and humidity. However, when dew point is reached, condensation can occur, potentially damaging data logger electronics. To prevent this, place adequate desiccant inside the instrumentation enclosure to control humidity and keep the dew point below the temperature of the data logger electronics. Replace the desiccant periodically.
If sending the data logger to Campbell Scientific for calibration or repair, consult first with Campbell Scientific. If the data logger is malfunctioning, be prepared to perform some troubleshooting procedures. See:
Also, consider checking, or posting your question to, the Campbell Scientific user forum https://www.campbellsci.com/forum 
. Our web site www.campbellsci.com has additional manuals (with example programs), FAQs, specifications and compatibility information for all of our products.
Video tutorials www.campbellsci.com/videos 
and blog articles www.campbellsci.com/blog are also useful troubleshooting resources.
If calibration or repair is needed, the procedure shown on: https://www.campbellsci.com/repair should be followed when sending the product.