Electrical headaches

I have a 2007 Tacoma 4.0/6 speed, 4WD and need your help with small electrical problems.
1, The horn doesn't work. I have changed the relay and the 10A fuse under the hood.
2, The fan motor doesn't work. I have changed the relay and 15A fuse (marked A/F HEATER?) under the hood.
Both the horn & the fan failed previously and then worked again after a brief period without doing any repair other than removing and inspecting the fuses. They did not work directly after checking the fuses.
3, The Air Bag warning light has been on for quite some time. To the best I can remember the warning light came on after a very fast trip down a long a 4WD road.

 

You need to do some trouble-shooting to narrow down the problem. For example:

For the horn ... unplug the connector from the horn itself and see if it is getting power when your buddy pushes on the horn. Not sure about your 2007, but on my 1999, the ground is thru the body of the horn to the frame.

 

I bet you also have a horn relay. Please see the attached .pdf from the 2007 SLI.