RMPU Filters

Shown here are Fresh and Return Air Filters of non-LHB RMPUs.

Some questions are:

What is frequency of change?

How best to clean these Filters?

Harness Couplers in Coaches

In pre-2011 coaches we used to have this kind of arrangement:

 Front side is power cable, back side is the control connectors.

 These days we have harting connectors for both power (440V) and control 110V connections to RMPU

 Recently we found some harting couplers failing in new coaches.

Inside view of the harting connectors.
Should we re-designh these connectors or simply relocate them to prevent failure due to water ingress?
See how they have failed:

Era of open type compressors coming back?

After horrible experience with sealed type compressors ( FRPCPY >15) in AC systems, we now see latest coaches being rolled out by RCF with open type compressors.
These new coaches are having RMPUs fitted with HOB make open cimpressors which are basically inspired by DMRC experience.