Air horn solenoid valve

Did it ever work since you bought the coach?

What model, year coach...more info please.

Is it a Hadley solinoid?

Are you sure the old solenoid was bad? Disconnect the air line and have someone hit the horn to see if you can feel the solenoid click. Also check for air at the line. If no click or no air, the problem lies elsewhere.

RU getting an air supply to the horn, if so the horn is clogged or it is out of adjustment

I replaced mine about a month ago and it was the culprit.

More information will help-- what coach, what year?

Does the valve get its 12 VDC positive through a fuse AND a relay-- if so, verify that you have 12 VDC to the solenoid (assuming the horn button is ground-- don't know since we don't know what you have).

If the horn button IS ground, run a jumper wire from the ground terminal of the solenoid to a good solid piece of metal on the frame. Let us know what you find and what you have.

Check the ground connection?
Are you getting power to the solenoid?
Can you operate your solenoid by pushing the plunger to make horn work?
I am betting on ground problem!
What is make and model of the solenoid you installed? Make and model of old solenoid?