Hi padair

ive never had it.. always had a line and it meant positive.. but as far as i am aware if you read it within the said time frame it is unlikely to get a fake positive or evap lines.. That being said you say some havent shown up till after 10 mins.. are you always using FMU? it seems pretty unlikely that you would get 10 evap lines and it actually still be a negative..

not sure if that has helped lol