I believe everything Filipe said is correct.  If you're still having trouble, it might be worth looking at a raw Solr query with debugQuery=true on the URL to see if that gives you any additional information.  I believe that sometimes multi-word synonyms can cause weird results because of the way they interact with tokenization.

- Demian

From: Nathan Tallman [ntallman@gmail.com]
Sent: Tuesday, October 30, 2012 11:00 AM
To: vufind-tech
Subject: [VuFind-Tech] Solr synonyms.txt Question

If I add the following line to solr/biblio/conf/synonyms.txt:

HUC,"Hebrew Union College"

Will VuFind return results including "Hebrew Union College" when a user searches for HUC? This is my understanding of synonyms.txt, but I'm not getting the expected behavior after restarting. So, maybe I'm wrong!