The Access Point cannot be converted to Mobility Express due to the er

[Valdani]

I am using Cisco Aironet 1852 device. When attempting to change from CAPWAP version 17.9.4.27 to Mobility Express, an error message "Not Enough Space" is displayed. In the Primary and Backup boot sections, I am using version 17.9.4.27. How can I delete files to make enough space for uploading the Mobility Express image?

[marce1000]

   -  Have a look at https://community.cisco.com/t5/wireless-mobility-knowledge-base/erasing-flash-and-reloading-the-access-point-image-on-cisco-ap/ta-p/3161648#toc-hId--1443336670 
                   Change directory names which you no longer need accordingly ,

 M.

[balaji.bandi]

check this thread :

https://community.cisco.com/t5/wireless/upgrading-me-access-points/td-p/4408710

[Rich R]

You're trying to install 8.10.130.0 ME - why?  That's very old!  You should be using 8.10.190.0.

If you haven't succeeded yet then try installing the 8.10.190.0 CAPWAP image first, possibly in both partitions by installing it and then installing it again.
https://software.cisco.com/download/home/286285803/type/286288051/release/15.3.3-JK10
Then convert to 8.10.185.0 ME (seems to currently be the latest version for 1850 - 8.10.190.0 is missing, have reported it):
https://software.cisco.com/download/home/286285803/type/286289839/release/8.10.185.0

If you still see the same error I don't think there's much you can do because you cannot easily delete files from the partitions manually and Cisco has not published the u-boot recovery images for these APs which are needed for a complete re-flash.  In that case you might need to consider RMA.