SharePoint 2013: Unexpected response from server. The status code of response is ‘500’. The status text of response is ‘System.ServiceModel.ServiceActivationException’ Null

Solution 1

Reduce the Search Service Performance Level with this PowerShell command:

Set-SPEnterpriseSearchService -PerformanceLevel Reduced

Set-SPEnterpriseSearchService -PerformanceLevel PartiallyReduced, which is in between reduced and Maximal

Solution 2

Limit the Memory Footprint of NodeRunner.exe is one thing that is not so recommended. There is a configuration setting for NodeRunner.exe’s configuration file that can limit RAM usage of a single process to specific value in megabytes.  This configuration file is located at: C:\Program Files\Microsoft Office Servers\15.0\Search\Runtime\1.0\noderunner.exe.config.  The configuration setting is under the nodeRunnerSettings node and it’s called memoryLimitMegabytes.  Its default value is 0 (unlimited).  Every time you change it, you’ll need to restart all of the noderunner.exe processes.