Nissan Repair: Sentra Horn not working, steering wheel, loose wire

Question
QUESTION: The horn on my 2001 Sentra is not working.  The horn itself is good with 12V going in.  The relay and fuses also seem good.

The problem seems to be that the voltage at the relay is only 5V for some reason.  Its 12V at the fuses, but only 5V at the relay.  According the wiring diagram there doesn't seem to be anything between there.  What could be causing this drop?  (The 5V is very consistent.  doesn't seem to be a loose wire).

ANSWER: Andrew,

If you bridge the relay I would assume the horn works?  It appears the horn pad is defective and you are not getting enough power to close the horn relay contact points.  The connection at the steering wheel could be the problem where the brushes contact the back of the steering wheel.

---------- FOLLOW-UP ----------

QUESTION: No, bridging the horn relay doesn't work because that only sends 5V to the horn, which apparently isn't enough to make it work.

The steering wheel connection seems to close to ground correctly, but the incoming voltage to pings 1 and 5 of the relay is only 5V for some reason.

Answer
Andrew,

Then you are going to have to start on the other end.  From the steering wheel, remove the column cover, pull the harness and start probing the wire.  But, I am pretty sure you will find the resistance that is dropping the voltage to five volts at the connection from the steering wheel to the contact ring under it.  To remove the steering wheel is going to be a pain.  You need to remove the airbag.  This is dangeous and if you are not familiar with their operation you might want to take this to a shop.  That is a pain to get off.  You have to disconnect the battery, then the airbag fuse, then the airbag connection at the steering wheel.  Wait five minutes to allow the airbag capacitor to bleed off.  Then, remove the airbag and keep your body away from the operating end.  Unplug and then place where it cannot deploy, face up.  Now, remove the center nut and using a steering wheel puller, remove the wheel.  Once off you will see where the horn contacts are.  This is probably where the problem resides.  But, again, first pull the column cover and check the power at the harness to make sure that is where the problem resides.  The only other place the harness connects is at the fuse block where power comes from. But, that is from a buss bar and the probability of a loose connection there is way out.