Step by Step Guide to delete old ACS Forwarders

1. Stop the ACS Collector Service on the related Collector Server.
2. Delete the old ACS Forwarders from the acsconfig.xml file.

C:\Windows\System32\Security\AdtServer\acsconfig.xml

3. Additionally delete the old ACS Forwarder Information from the OperationsManagerAC database like in the example below.

delete from [OperationsManagerAC].[dbo].[dtMachine] where id in (1,2,3,4,5)

4. Start the ACS Collector Service.
 
Good luck !