S80 running hot-2009
 

Replaced sensor and thermastat housing, but still getting "high temp" message. No leaks and fan works. Only runs hot in stop-n-go traffic in the evening. Also, runs hot when I use defrost instead of AC during rain. Never runs hot in the morning. Red light stays on until fans stops running or car cools. No one has figured out problem in a month. Help!!! Mom with 2 kids needing to get picked up on time!