Bogus Air Horns

[hax]

Sometimes my air horn honk as air horns should, but mostly they just squeal.
I've checked the pressure in the air system, and the emitted tone does not seem to be a function of air pressure. I can get a squeal or a honk at 120 psi as well as a honk or a squeal down to about 60psi. Below 60psi it is pretty much a squeal.
I can feel the solenoid click when the horn button is pushed so I'm assuming that it works and that it is an open or closed valve, rather than a variable flow valve.
Does anyone have any suggestions?

[LJowdy]

Remove the air line and have someone press the horn button/ring. See if you're getting sufficient amount of air to pass through the line. You can hook up a PSI gauge but just try the test above first. If you're getting sufficient air "every time" (You may have a bad valve) then the problem may be with the horns themselves. Personally I think it's an air supply issue. But also remove the horns and make sure no crud is lodged in the air inlet nipple on the horns. If something is stuck inside, it could periodically block the air going to the horn thus the odd noises you hear.

[hax]

An update to my bogus air horns. I first replaced the solenoid, but that did not solve the problem. So I removed the horns and rigged a pressure gauge up to the air hose at the horns and found out that I was getting around 110+ PSI to the roof. Next I took the air horns apart, and one of the horns had a small cork gasket fall out from between the trumpet and the sound box and other horn did not have a gasket. I took apart the sound boxes and the springs had some minor rust, but the diaphragms were clean. I tried to call Grover CS several (4) times to ask for trouble shooting tips but never got a return call. A Sound box repair kit is $36 + shipping from Grover so I tried to use a similar sized fiber washer from Ace. The outside diameter was the same size, but the inside was smaller than the cork gasket and it was very stiff and thicker. It did improve the sound of the horn, but it still started honking with a squeal or drift into a squeal. I broke down and bought repair kits from Amazon for $27. Installing the new cork gaskets between the trumpets and the sound box greatly improved the horns. The horns are tuned by how close the trumpet is to the sound box. I have some concerns about the distance between the solenoid and the air horns. I have about 12+ feet of 1/8 inch hose between the solenoid and the horns. I don't know if that run is to long to carry sufficient air flow to the horns or not, and that might be why WRV placed some of the solenoids behind the upper cabinets. I also think that the older coaches with the air horns on the front of the cab probably get buffeted and that is what destroyed the one cork gasket. But for now I can honk at the little blue car that pulls in front of me.

[guardrail53]

Hax, have you checked the trumpets for debris, bugs, birds, leaves, dirt, sand, and all the other stuff that comes out of them when you have someone honk them as you tap on them with a wooden handle? You would not believe what you will get out of them! Can't hurt to try? Rail!