Does the A/C system in the 05 TL have any kind of pressure relief valve?

 

 

You'll find it on the compressor.

 

Did you overcharge / recharge the system???

 

Unfortunately, yes. I've done this several times and am comfortable with the process. I was showing my son how to do it (system was low on coolant) and I'll be damned if I forgot to turn the A/C on while recharging. After realizing the error I turned A/C on and observed the coolant pressure gauge immediately peg out and loud hissing (which I now know was coolant venting) from the area of the compressor. Immediately turned car off and relieved pressure from return line until it dropped to within spec. Does not appear anything adverse happened as it is still blowing cold a couple months later.