i have a 1991 firebird and my heater will run for a couple days just fine or sometimes only for like 20 min. My fuse pops all the time and i can not figure out what is causing it (it usually pops when im driving, seems like sometimes hitting a bump causes the problem. weve changed the heater blower motor, weve replaced the heater controls, and weve looked but cant seem to see anything wrong like wires or anything that could be causing it and even by the fuse box everything looks ok. anyone who has had this happen to them or has a pretty good idea where or what would be causing this or the best places to check would really be helpfull. thankyou.