Volvo Air Horn not working

2020 Volvo VNL 760 air horn located above batteries, under the cab. Don't confuse it with city horn.

1. Check fuses F20 Horn and F33 Air Solenoid Switch 

2. Unplug the red 1/4 air hose coming to the horn, plug it with your finger while pressing the air horn actuator (air bag) on the steering column.

 - If air is coming from the hose - replace plastic horn.

 - If no air coming to the hose - proceed to the next steps (electrical signal is not pushing air through solenoid for some reasons).

3. Unplug the left solenoid (with red hose) and measure 12V coming to it while someone else have to press the horn actuator (air bag) on the steering column. 

Four solenoids are located under the center of the truck on a cross member, facing back.

  - if 12V is coming to the solenoid - replace left solenoid ($100 part and 40 mins work).

 - if 12V is not coming to solenoid - proceed to the next steps (wire issue somewhere above).

4. Replace Clock Spring in steering column. Chances are it's were the wires are broken. Here's good video explaining how to do it. 30 min project and $90 part. 

https://youtu.be/424nOz2Ao44

5. If the problem is still there - the wire that transmits electrical signal is damaged somewhere. Keep searching for it.