stupid question maybe but your being sarcastic right as you fill it up via the expansion tank so obviously the cap has to be off....

my heater works but not very much. it will blow some hot air but as soon as i turn it on to full power the air goes colder but still noticeably warmer than when i turn it to cold.

when the fan is off and on hot setting i get the usual breeze of hot air through the vents. ( i can't close vents completely cause i have nomad gauge holder there!)