Can you tell me which relay is for the horn on a 2009 Equinox

USA SPEC CAR ? (MEANS SOLD THERE FIRST) OR VIN TELLS THIS.
I read the SM, service manual to you, horn schematics.
on 2009 cars, best is check all fuse just in case network errors are cause.
ok no BCM here.
so yes the relay clicks , and closes and honks the horn
shows 2 horns but using ground a23 and a24, got rust there>?
the fuse drives a fuse called HORN
10amp
if you do a 2 mean test, and gay1 honks, and guy2 listens to horn really and you hear it click , that tells you 2 things, horn button good
and CLOCK spring, horn pin not broken
and like magic if it did click, now you found it using EARS.

the book says
engine room R/B and J/B (horn relay)
engine bay fuse box has the relays. not cab.
again USA car left hand drive, not UK or other RHD cars.world wide

If it's blowing fuses, you probably have damaged wiring to the horn, not a bad relay (relays generally fail open rather than with a short to ground). Find the horns (GM usually uses two horns to play a chord), and inspect the wiring to them. Look for a bent terminal shorting to ground, or some spot on the wire where the insulation has been cut or worn by contact with metal. In particular, if the car has been in an accident, check the areas where there was body damage (if the horn relay was bent up by an accident, that may be an exception to the general case that relays themselves don't usually blow fuses.

first, an owner should always have a service manual
or an operators manual at a minimum
http://www.vadengmpp.com/owners-manual/buick/1998-Buick-Lesabre.pdf
the horn is fuse #3 on page 6-58
there is also probably a horn relay to consider.

With the key on but not the engine, press the horn ring a listen for a click, that click is a horn relay. You may need someone to listed under the hood for you, If you don't hear the click, take the covers off the fuse box and see if there is a diagram for the relays that shows a horn relay. While you are checking, look for a fuse for the horn. In rare cases it could be the horn ring or the clock spring.

The relay should be in the fuse box. fuse box may be located under the hood. or under the passenger side dash down by your feet.

Where is the fuse for the horn located in a 2005 Chevy Equinox?

In your owners manual go to the index and look for fuses then go to that page. Look for the horn fuse which should be in the fuse box under your hood around your engine, in your owners manual is should tell you where it's located. Find the fuse for it by looking at the diagram on your owners manual and then pull that fuse out. You should have replacement fuses in the fuse box that's in your car, you have to open the car door to get to it. If you don't have that fuse just take it up to auto zone and tell them you need a replacement for that fuse.

If u look in your owners manual you should see a diagram of the fuses and their purpose for each! The fuse box is located under the hood on the drivers side,next to the radiator resevoir.there are depression clips that hold down the top of the box on each side, depress them and lift off! You should see the fuses but they only have numbers on them, cross reference them to the diagram in your owners manual. hope it helps

its one of two things,check your horn relay or your horn switch is not getting a ground,you can check this by grounding you relay