SharePoint Fast Search error: The remote server returned an error: (503) Server Unavailable.

When I go to my app server and go to the fast search service application I see this error:

The remote server returned an error: (503) Server Unavailable. 

when I click on "Content Sources" I got this error:

Error 
System.Net.WebException: The remote server returned an error: (503) Server Unavailable. 
  at Microsoft.Office.Server.Search.Administration.SearchApi.RunOnServer[T](CodeToRun`1 remoteCode, CodeToRun`1 localCode, Boolean useCurrentSecurityContext, Int32 versionIn) 
  at Microsoft.Office.Server.Search.Administration.SearchApi..ctor(SearchServiceApplication application) 
  at Microsoft.Office.Server.Search.Administration.SearchServiceApplication.get_SearchApi() 
  at Microsoft.Office.Server.Search.Administration.ContentSourceCollection..ctor(Content parent) 
  at Microsoft.Office.Server.Search.Administration.Content.get_ContentSources() 
  at Microsoft.Office.Server.Search.Internal.UI.WebControls.ListContentSourcesControl.OnLoad(EventArgs e) 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Control.LoadRecursive() 
  at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) 

Troubleshoot issues with Microsoft SharePoint Foundation. 

Correlation ID: 14bd193e-8c65-408a-b7ae-0fc6dc5f0af7 

Date and Time: 10/12/2014 09:52:44 

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What is going on? I dont know why I got this error!