Install windows update

I have following powershell script which should update my windows OS everytime I run it. Therefore I use the given windows API in order to search, download and install the updates. But somehow only searching for them actually works.

This is my script:

$global:scriptpath = $MyInvocation.MyCommand.Path
$global:dir = Split-Path $scriptpath
$global:logfile = "$dir\updatelog.txt"

write-host " Searching for updates..."
$session = New-Object -ComObject Microsoft.Update.Session
$searcher = $session.CreateUpdateSearcher()
$result = $searcher.Search("IsInstalled=0 and Type='Software' and IsHidden=0")

if ($result.Updates.Count -eq 0) {
     Write-Host "No updates to install"
} else {

    $result.Updates | Select Title

}

$downloads = New-Object -ComObject Microsoft.Update.UpdateColl

foreach ($update in $result){
    try {
        $update.AcceptEula()
        $Null = $downloads.Add($update)
    } catch {}

}

$count = $result.Updates.Count

write-host ""
write-host "There are $($count) updates available."
write-host ""

read-host "Press Enter to download\install updates"

$downloader = $session.CreateUpdateDownLoader()
$downloader.Updates = $downloads
$downloader.Download()

$installs = New-Object -ComObject Microsoft.Update.UpdateColl
foreach ($update in $result.Updates){
     if ($update.IsDownloaded){
           $installs.Add($update)
     }
}

$installer = $session.CreateUpdateInstaller()
$installer.Updates = $installs
$installresult = $installer.Install()
$installresult

But I get following error:

Exception calling "Download" with "0" argument(s): "Exception from HRESULT: 0x80240024"
+ $downloader.Download()
+ ~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : ComMethodTargetInvocation

Somehow this line: $downloader.Updates = $downloads is not executed, but I don't know why. I also already tried running the script as an admin, didn't work either.

That error code is the WU_E_NO_UPDATE, described here. Basically it says that the Updates collection is not set or empty.