What should I do?

I'm going to install wall lights on the outside of my garage. The existing wires protrude out the siding and coiled. I don't know if it has a metal box behind the siding. Should I cut a small hole around the wire to see, or can I hang the light the way it is? The lights are fairly large, 14.5 inches high. A rookie here, any advise would be appreciated. Thanks

 

You need a box to install the lights unless they have a built in connection box which is unlikely. If you don't have a box you need to install one. An old work round box should work if you can't access the back of the wall. If there is a box covered by siding the siding needs to be cut away and an extension ring added. Depending on the type of siding a mounting block with built in connection block may be easier then adding a box.

Mounting block example: Online Catalog | Siding Mounting Blocks | Siding Mounting Block

If this is work you just paid a contractor to do he needs to come back and finish the job.

 

If you just have wires protruding from a hole I am willing to bet that you do not have an enclosure in the wall. You should be able to tell without cutting by shining a flashlight into the hole where the wire protrudes. You should be able to see evidence of a metal or plastic enclosure.

You say your lights are large. How heavy are they? I've mounted normal size lights, probably up to what you have, to a surface mounted vinyl siding enclosure like Ray2047 linked and had no trouble. One thing to keep in mind is how large the base is for your light. Often, fancy lights have a large decorative base that is larger than most pre-made vinyl siding boxes like this:



In those cases I measure an area big enough for the fixture's base and cut out the siding oversized by at least several inches. Then I mount an old work box in the wall and use a sheet of vinyl siding trim stock to cover the hole with generous overlap underneath the existing siding. Then I trim out the opening with J channel. Make sure to caulk the seams where the trim stock and J channel meet so water cannot get behind the siding.

 

My fixture weighs almost ten pounds. I have noticed a couple of different boxes, which one would be the best for this fixture assuming there is no box under the siding and maybe no 2x4 close by. Thanks

 

That depends on what is under the siding. If the wall is sheathed with OSB, for example, you should be able to mount a box strongly enough to support the light. Just make sure that the front edge of the box is flush (within 1/8") with the face of your mounting surface.

 

If your fixture has a larger backplate like shown in PilotDanes photo you can use one of these.

Online Catalog | Siding Mounting Blocks | MEGA Siding Plate

AFAIK, the box portion is the same as the block in Ray's link, only the exterior plate is different.