I had a strange fuse symptom yesterday. After picking up my 300D from my indy (tranny service, etc), I noticed that the tach wasn't working and assumed he knocked something off. After it warmed up I noticed the ACC was giving me full heat regardless of the temp wheel setting. Everything else on the ACC worked fine.

When I got home and checked the fuses, I found the #14 fuse failed. After replacing the fuse everything was back to normal. The strange part was that the fuse failure resulted in the ACC going to full heat without any other issues.

So, if you get full heat from the ACC, check your #14 fuse. Strange.