My air horns have quit working. I do not know where to look for the relay and air horn solenoid. I noticed on a much earlier post that on a 1991 U300 it was on the back of the air gauge. Is that true for the 1991 GV as well?
Yes
On mine the PO installed an auxiliary knob under the dash that opens a 1/2" ball valve connected to the one of the main air tanks in front, and this runs a 4 pipe diesel locomotive train horn mounted in front. When needed it gets the job done...I don't really use the roof horns much...
Got to have the horns to pass inspection.
Found the solenoid where advertised. Found the problem. The power side crimp-on connector was not properly crimped and had come loose.
Excellent find John! Isn't this forum wonderful!