Need help with a 12v air horn with relay and momentary switch

S0AR3R · Mar 30, 2023

Hi I’m stumped and can usually figure it out after a while but not on this one. so I joined here In search of some help on my 05 tundra I’m putting an air horn on. It has two mini 12v compressors on it with two 30amp relays. 30 on relays going to air horns, 87 going to a fuse then battery, 86 jumped to 87 and 85 going to switch. This is where I get lost so I grounded my switch thats also led to the fire wall in the truck. then ran my blue wire from the switch to my 85’s (which is constant 12v) and I’m lost on what to do with the others I tried every witch way at this point. I just want the switch led to come on when the keys on and off when it’s out. so I put the switch ground to 12v ignition (on a 15amp fuse) and positive on switch ground on firewall. Then the green wire 12v ignition and I could only get it to work when my truck is off or my 15amp fuse is pulled. Like I said I tried wiring up this switch all different ways so if any one can help I very much appreciate it!
My switch

Mubashir39 · Apr 7, 2023

S0AR3R said:
Hi I’m stumped and can usually figure it out after a while but not on this one. so I joined here In search of some help on my 05 tundra I’m putting an air horn on. It has two mini 12v compressors on it with two 30amp relays. 30 on relays going to air horns, 87 going to a fuse then battery, 86 jumped to 87 and 85 going to switch. This is where I get lost so I grounded my switch thats also led to the fire wall in the truck. then ran my blue wire from the switch to my 85’s (which is constant 12v) and I’m lost on what to do with the others I tried every witch way at this point. I just want the switch led to come on when the keys on and off when it’s out. so I put the switch ground to 12v ignition (on a 15amp fuse) and positive on switch ground on firewall. Then the green wire 12v ignition and I could only get it to work when my truck is off or my 15amp fuse is pulled. Like I said I tried wiring up this switch all different ways so if any one can help I very much appreciate it!
My switch

View attachment 107220

Check your car fuses using a multimeter to ensure they are properly connected and functioning.
Refer to a guide on how to check car fuses with a multimeter, using your backlink: How to check car fuses with a multimeter or battery tester? - https://multimeterworld.com/how-to-check-car-fuses-with-multimeter/
Make sure you have the correct power source for your switch and LED.
Connect the switch ground to a 12V ignition source and the positive on the switch ground to the LED, then connect the other side of the LED to a good ground.
This should allow the LED to turn on when the key is on and turn off when the key is off.
If you're still having issues, consult a wiring diagram or seek assistance from a professional mechanic or automotive electrician.