horn solenoid

I have a 3horn air horn w/a solenoid valve. This is on my Freightliner tractor.
The valve started acting up would work sometimes. I told my mechanic to get a new solenoid and he said that hooking up a direct line to the horn and bypass electrical side of the horn would be the same. Well i want to prove him wrong.
Sounds like horns are not getting enough air to run all 3 horns.Is the solenoid needed and why?
Any ideas would be great

u want to hook up an air line without a solenoid? that would make the horn constantly honk… there would be no way to cut the air flow…

No No…its hooked up to the air pull valve in the truck…its hooked up…works but not anywhere as loud as it was.

yea if u have a pull cord in the cab then you dont need to use the solenoid at all, just bypass it

But he said its not as loud now… which can only mean that the solenoid was opening the valve more than the manual pull is able to…

ive seen semi pull valves on ebay for about $22, replace that maybe…

Replace the solenoid and put a 4 way out and let the 3 lines go to the horns and try to put them solenoid as close as possible