Usually any line, no matter how faint is a negative. Now in my testing experience a really faint line means you may be borderline for a more sensitive test that they would send to the lab for confirmation. If it were me I would follow the dilutuon sticky as a backup and substitute with the Quickfix. That way your not risking anything that is close. Not sure why the temp is a problem. Follow the directions. Temp will be right around 96-98. Good luck. let us know how it goes.