Occasionally there will be instances where you need to remove a server from the Search Service Application, if you have multiple search servers set up in the farm. To do so, especially if the server is unavailable, or offline, follow the steps below:
$ssa = Get-SPEnterpriseSearchServiceApplication $active = Get-SPEnterpriseSearchTopology -SearchApplication $ssa -Active $clone = New-SPEnterpriseSearchTopology -SearchApplication $ssa -Clone -SearchTopology $active $clone.GetComponents() //use the output from above to grab the names of each component from the server you wish to remove. remove each component as necessary. Remove-SPEnterpriseSearchComponent -SearchTopology $clone -Identity ($clone.GetComponents() | Where-Object {$_.Name -eq "ContentProcessingComponent3"}) -Confirm:$false //check the new components topology $clone.GetComponents() //set the topology Set-SPEnterpriseSearchTopology -Identity $clone