param([string]$ContentSourceName="Local SharePoint sites")

Add-PSSnapin Microsoft.SharePoint.PowerShell –ErrorAction SilentlyContinue

 # (Get-SPEnterpriseSearchServiceApplication).reset($true, $true) # full reset


#Get Search service application
$ssa = Get-SPEnterpriseSearchServiceApplication 

#Content Source Name
Write-Host "reset indexes of :  $($ContentSourceName)"

 

#Get the content source 
$ContentSource = Get-SPEnterpriseSearchCrawlContentSource -Identity $ContentSourceName -SearchApplication $SSA

 
 #Get Each Start Address
$StartAddresses = $ContentSource.StartAddresses | ForEach-Object { $_.OriginalString } 
 

#Clear Indexed content starts with custom contnet source
$ContentSource.StartAddresses.Clear()
 

#Re-add the start address to content source
ForEach ($Address in $StartAddresses ){ $ContentSource.StartAddresses.Add($Address) }