furnace vents not getting air

I turned on the furnace for the first time last week to just check it before we go camping this fall. It kicks on and sounds fine, but you can only feel heat, or anything for that matter, coming out of 1 or 2 of the vents. I haven't had time to fool with it yet, and wanted to get some tips before I did. I thought about making sure the ducts from the furnace to the vents were clear by maybe blowing some air through them. Any suggestions or has anyone else had this problem. I have a Sundance 310QB and it doesn't have the vents in the floor.

Thanks ahead of time

I had the 2 vents in the back that had come loose from the furnace plenum. I opened the furnace area and re-attached them and secured them with foil tape. The duct take-offs are metal pieces that insert into the holes and are then twisted to "lock" them in. When they insstall the flex duct first the flex wants to turn back to the original shape and pulls the adadpters off.

Vents & Hoses...

Check hoses for kinks and for being loose. Not a unusual problem. GBY...

In our 3670, the majority of the furnace airflow comes out of the bathroom and bedroom vents. Being higher and having few windows, that's the last place we needed the heat. These are the nearest to the furnace and therefor have less static resistance. We replaced those two vents with closeable vents from Lowes. I also got into the belly and straightened some of the kinks out of the flexible ductwork. I also had some debris in the rear vent duct. All of the above corrected the air distribution problems. Just be sure not to close off too many vents, as this will cause higher temperatures on the furnace heat exchanger and can cause tripping of the high limit switches on the furnace.
Good Luck.

WE had very weak air flow. Found that 2 of the "blank" hole covers came loose from the plenum. I reinstalled them with sheet metal screws. I did while I was in there, install screws in the ones used for the duct work. I did replace 3 registers with the dampners. This is a good source for them. Bob http://dwincorp.com/index.php

Thanks for all the advise. I plan on trying to work on it over the next week.