Bmw e39 520i year 99 horn problem?

when i press the horn it dos int work i have checked all fuses but no joy i have taken out the double horn tested it on a 12v power and they bought work fine the problem is when i press the horn the air bag light gose dim as the airbag light says on all the time anyway and when i do press the horn i can here something clicking as if it is a relay but cant seem to find it it seeming to be coming from the left side of the engine is there relays under the pollen filters also when i slide the sun visor the lights dont work and the radio turns off any ideas would be great