I've had a similar issue with my refer. The refer was ~14yrs old. Just died on a weekend trip. Gas would light, No issues with 110v or 12v. Got some gurgling, chimney got hot and didn't see any yellowing effect or smell any thing. Decided to pull fridge and found that the leak was in the chimney and found a ton of yellow staining. Once I got the fridge out, boy did it STINK!! My guess is that the ammonia made its way up the chimney due to a draft effect. Simple but costly repair.....Replace refer.
-paul