when i got my car used, i tested it and i THOUGHT there was something wrong with it. it didnt feel like it was powerful enough. what i found out was that it is only slightly warm to the touch and the top lines are for the radio. i thought there was something wrong cause coming from my 95 chevy lumina, that thing gets really hot and can literally melt off snow and ice. guess its different for hondas, or newer cars in general..
If a few bars work, but some don't, there's probably a break in the line somewhere on each part that doesn't work. There are kits that essentially consist of metal suspended in liquid that you can use to repair the breaks. Just mask off the area around the break, paint, and let dry.
Even when it it does work, it's still a bit wussy. My Accord doesn't really put out much heat until you're moving (that goes for the blower, the seats, and the defroster all together)... I'll have to make a thread about it one of these days.