<!-- from fixya rte -->How to install cylinder on Rigid nail gun - Ridgid 2 12" Angled Finish Nailer R250AFA NEW

Have you kept it properly oiled?

If your using refills that have wire holding the nails together.
Check to see if bits of wire, debris is collecting in around the striking hammer. I switched to paper and never looked back. Must have gone through 5k worth of nails and rarely jams. Other things to check,
1. Check the striking hammer, make sure it is not bent or damaged.
2. Check air pressure, Low pressure can cause jamming, misfires.
3. If the tool needs pneumatic oil, 2-3 drops before you start good rule of thumb.
4. Check spring return. Sufficient pressure must be maintained or the nails will not feed properly. Misfires, incorrect feed, jamming etc.
I had a Hitachi brad nailer and it was horrible. Fire 1 brad nail would jam or misfire. Did everything I could think of nothing worked. Put it up, got a Rigid brad nailer and never looked at the Hitachi again. :)
Sometimes you just get a lemon! (PS I understand you have a framing nail gun. Brad nail gun above is used for an example)
Hope this helps

Try removing stuck nails without taking apart gun. Remove remaining nails from rails. Use long piece of allen wrench or similar hard steel and grind the end to allow for jamed nail (I use a broken driver blade ground slightly thinner to allow for stuck nail). Use heavy brass or copper hammer to push driver up to top of cylinder. If after a couple of heavy blows the driver does not move, remove the head of the gun and pull out the cylinder and place the body of the gun on plywood. This will protect the head from damage. Good luck

Remove nails and use thin tool to push driver all the way up to top of cylinder. If the gun fires one nail then skips, the driver is not returning to top of cylinder. If no nails fire, then nails are not feeding into proper position. Driver must return to top to allow nails to feed into position. Most common problems are bent driver, worn piston oring and bad batch of nails(head too large). Good luck

You have a obstruction in the path of the plunger taake it apart and clean it.

its probably the capacitor #079027007072 $10.58

A nail gun works on compressed air.
When you hook the air hose to the gun it fills a cylinder with air pressure.
When you pull the trigger. the cylinder pressure is released onto a firing pin that shoots the nail.
The air pressure line is also connected to the trigger and therefore the trigger has to be sealed.

When ever using a nail gun, you add a bit of gun oil in the back of the gun (not 3-in-1motor oil, it has to be non-detergent gun oil)

If you haven't used the gun in a while, it is best to oil up the gun and let the oil run down into the gun.
If you use anything but gun oil, the seals will give out.

Your trigger seal has given out. It is probably an 'O' ring. You can access it by taking it apart. Look for the O ring.
Bostich makes re-build kits for the different guns that you can buy on-line.
Back when I was in construction, there were several nail gun shops that sold and serviced nail guns, and sold nails to the contractors. I don't know if that business model is still active or if you have to send the guns to Bostich service center.

when pressed down the main switch is activated, so switch could be faulty or connections loose

If the piston/driver is broken, the gun will fire however nailing will not take place because the piston will jam in the cylinder. Sometimes the cylinder will also crack when the driver goes. If the piston is not broken but stays down, then check the cylinder check valve, worn lower bumper, bent driver or cracked cylinder. 18 guage nailer has a very thin driver which will easily bend or break. Parts however are not expensive.