Air Conditioning - Separating HVAC duct pieces?

The HVAC in our house has two routes: an upstairs route and a downstairs route. Each route has a open/close "switch". The switch to the downstairs route broke. How can I separate the duct pieces so I repair the switch? The duct pieces are held together by folded edges. Is there anyway I can take them apart and put them back together myself? Are special tools required?

Thanks

E Steve K

The 'switch' you're referring to may be what we call a damper, operated by a zone motor. Some zone motors have manual openers on them-a sliding lever or turning knob.
Is this what you are referring to?
Rarely does a damper in the duct 'break'.
Tom Beer 4U2

HVAC Mech
It's not that good a system. These "switches" are manual. There's a panel inside the duct with a rod through it that protrudes through the duct. On the outside, there's a handle attached to the end of the rod. Somehow the the panel got disconnected and apparently fell flat since air still flows through the duct and upstairs. I got to get into the duct to repair it.

E Steve K

OK, that's a manual damper. The duct is held together by what they call 'slips'. They allow a male/female type of connection. Here's a look: SIDE VIEW
http://i59.photobucket.com/albums/g314/tomd7735/Slips.jpg
One duct will pull straight out of the other, once you remove any screws. 1/4" or 5/16" nutdrivers or a hex bit for the drill is usually what I use. The screws may be slotted, though.
To get enough play to pull the duct far enough, you may have to disconnect some duct hangers, and maybe even drop an elbow from the end of the run.
Then you should be able to reach in far enough to replace the damper blade on the shaft.
Tom Beer 4U2

Or, with tin snips, cut an rectangular access hole into the side of the duct, reach in and repair, then cut a piece larger than the hole, screw it and seal it with aluminum tape. Not duct tape. Duct tape will disintegrate.
Tom Beer 4U2

HVAC Mech

I might have to go with your second suggestion. The sections of the duct do not pull apart. The edges/lips of the duct sections are folded into one another in a complicated way and there are no screws. Have you ever come across this kind of arrangement? When I tried to pry the folds apart, they get twisted and look like they'd never correctly go back together again.

Thanks

E Steve K

Sounds like the sections were made in the shop with a lockformer machine. When fit together on the job site, a lip is hammered over. Some of the ones I've seen can be opened with a hammer used to drive a screwdriver sideways down the seam, opening the lip.
Maybe a sheet metal guy could add his ideas...
Tom Beer 4U2

that is a standard S and Drive system. Fold the ends of the drives up straight and hammer them right off and if you are careful you can reuse them. Once the drives are off the edges will slip out of the S's.

After HVAC Mech used the term "slip", I googled the phrase "slip duct" and was able to find the first picture at the following link:
Single-Wall Rectangular Ductwork from McGill AirFlow LLC (http://www.mcgillairflow.com/textDocs/rectangular/rectang_connect.htm)

I then went downstairs to the basement and found that I could slide the connector off sideways. All this time, i thought I had to pry them apart. What a revelation!

Thanks for the responses.

E Steve K