SharePoint Central Admin Accessibility (Unknown error Occurred) Application Server Administration job failed for service instance

 Application Server Administration job failed for service instance Microsoft.Office.Server.Search.Administration.SearchServiceInstance (GUID).

Reason: Logon failure: unknown user name or bad password

Techinal Support Details:

System.ComponentModel.Win32Exception: Logon failure: unknown user name or bad password at Microsoft.Office.Server.Search.Administration.SearchServiceInstance.SynchronizeDefaultContentSource(IDictionary applications)

at Microsoft.Office.Server.Search.Administration.SearchServiceInstance.Synchronize()

at Microsoft.Office.Server.Administration.ApplicationServerJob.ProvisionLocalSharedServiceInstances(Boolean isAdministrationServiceJob)

So you might have changed search service account manually, if you have changed farm admin account please run script mentioned in following article

this is the procedure to update farm admin account

How to change service accounts and service account passwords in SharePoint Server 2010

To change the passwords for service accounts in SharePoint Server 2007 and in Windows SharePoint Services 3.0, follow these steps.

Note If the Microsoft SQL Server service uses a domain account, and the password for that domain account is either expired or invalid, make sure that you update the password for the domain account first.

1.      Update the password for the account that is used by the Central Administration application pool. To do this, follow these steps:

a.      On all servers in the server farm, open a command prompt, type the following line, and then press Enter:

cd %commonprogramfiles%\Microsoft Shared\Web server extensions\14\Bin

b.      Do one of the following:

§  On the server that hosts the Central Administration website, type the following line at the command prompt, and then press Enter:

stsadm -o updatefarmcredentials -userlogin DomainName\UserName -password NewPassword

§  On all other servers in the server farm, type the following line at the command prompt, and then press Enter:

stsadm -o updatefarmcredentials -userlogin DomainName\UserName -password NewPassword -local

c.       Restart Internet Information Services (IIS) 6.0. To do this, type the following line at the command prompt, and then press Enter:

iisreset /noforce

2.      Verify that the Administration Application Pool Credential Deployment job definition is no longer displayed on the Timer Job Definitions page of SharePoint 3.0 Central Administration. To do this, follow these steps:

 .        Open SharePoint 3.0 Central Administration, click Operations, and then click Timer job definitions under Global Configuration.

a.      Verify that the Administration Application Pool Credential Deployment job definition is no longer displayed in the list.

Note If the Administration Application Pool Credential Deployment job definition is displayed in the list, wait until it disappears from the list.

3.      Update the password for the application pool account that is used by web applications on the server farm. To do this, type the following line at a command prompt on every server on the server farm, and then press Enter:

stsadm -o updateaccountpassword -userlogin DomainName\UserName -password NewPassword -noadmin

4.      Update the password for the account that is used to run the Windows SharePoint Services Help Search service. To do this, type the following line at a command prompt on every server on the server farm, and then press Enter:

stsadm.exe -o spsearch -farmserviceaccount DomainName\UserName -farmservicepassword NewPassword

5.      Update the password for the default content access account that is used by the Windows SharePoint Services Help Search service. To do this, type the following line at a command prompt on every server on the server farm, and then press Enter:

stsadm.exe -o spsearch -farmcontentaccessaccount DomainName\UserName -farmcontentaccesspasswordNewPassword

6.      If you are running SharePoint Server 2007, you must also follow these steps:

 .        Update the password for the account that is used by every Shared Services Provider (SSP) on the server farm. To do this, type the following line at a command prompt on every server on the server farm, and then press Enter:

stsadm.exe -o editssp -title SharedServicesProviderName -ssplogin DomainName\UserName -ssppassword NewPassword

a.  Update the password for the account that is used to run the Office SharePoint Server Search service. To do this, type the following line at the command prompt, and then press Enter:

stsadm.exe -o osearch -farmserviceaccount DomainName\UserName -farmservicepasswordNewPassword

b.  If the server farm is configured to use single sign-on, update the password for the account that is used by the Microsoft Single Sign-On Service. To do this, follow these steps:

1.      Click Operations in SharePoint 3.0 Central Administration, and then click Service accounts under Security Configuration.

2.      Under Windows service, click Single Sign-On Service.

3.      Under Configurable, specify the password, and then click OK.

c.       Update the password for the default content access account that is used by the Office SharePoint Server Search service. To do this, follow these steps:

0.      Open SharePoint 3.0 Central Administration, and then click the link to the SSP web application under Shared Services Administration.

1.      Under Search, click Search settings, and then click Default content access account.

2.      Specify the password to use for the content access account, and then click OK.