I have two 40 inch Grover air horns on the roof. They did not work. One reason is that the air to them is disconnected, the other appeared to be functional since I took one down to bench test. I opened it up and found that there is not much to them to go wrong, so I called Grover and spoke to Dave in tech support who told me how to, and also emailed, how to tune them. It worked great. Just posting this in case anyone needs that info.
Oh yeah, here's the info
Adjusting a GROVER STUTTERTONE or ORGANTONE HORN
While adjusting the horn it important to remember that what you are doing is adjusting a very small gap between the back of the bell and the front of the diaphragm that is contained within the sound unit
DIRECTIONS
1. Rotate the Sound Unit (fat part at back of horn) in a counterclockwise direction to loosen the horn.
2. Rotate the Bell/Bushing assembly (flared part where sound comes out) until there is approximately one thread at the front of the ring at the top of the rear mounting bracket. The bell may need to be rotated in either direction.
3. When the bell is in the proper position, hold the bell and the mounting bracket in place while you tighten the sound unit onto the back of the bell/bushing assembly.
4. Try the horn.
----If it sounds "breathy" with a lot of air sound, the back of the bell is too far away from the diaphragm. Loosen the sound unit and rotate the bell 1/8 turn clockwise to make more of the bell stick out the back of the mounting bracket. Retighten the sound unit and try the horn again.
----If the horn sounds "pinched or "squeaky", the bell is too close to the diaphragm. Loosen the sound unit and rotate the bell 1/8 turn counterclockwise to move it away from the diaphragm. Retighten the sound unit and try the horn.
6. You may have to loosen and adjust several times to find the best spot.
5. When you have achieved the optimum adjustment, the whole horn needs to be tightened while retaining the bell-to-diaphragm adjustment. Rotate the bell and sound unit AT THE SAME TIME to tighten the horn. If you are on standing on the right-hand side of the vehicle, this would mean grabbing the front and back of the horn and rotating it towards you until tight. Remember that you have to preserve the gap between the bell and the diaphragm by moving the bell and sound unit at the same time.
Lin- this looks good. Thanks for posting this to the group. I may even need this myself sometime soon. I hope.
:-)
Kind Regards, Phil
It worked on the horn I tried. The mechanism in the sound chamber, the housing on the back is quite simple; just a thin metal disk and a spring. There is also a gasket between the sound chamber and the collar. That's it. It is surprising how a small adjustment makes the difference between full sound and just a hiss of air.