So you have 3 alert files from your 3 node RAC and you are trying to see what happened in the cluster as a whole. The Rac Synchro Reader will let you view the alert files of all 3 nodes side by side, with the timestamps aligned. When you scroll one alert file the others will scroll to a matching timestamp.
Windows executable. Others have found it works with the Listener logfiles, too. Tested for alertfiles from version 9 and 10.