K5LA Truck horn blows before Train horn

Hello I have K5LA set for about 2 years it’s worked great. But it’s started not working unless I hold my horn down for several seconds. And sometimes it still never kicks in. I replaced the solenoid already and the prob is still there can anyone point me in direction I need to go to fix it?

Info I do have it wired in with my truck horn so no toggle switch as far as to work the train horn. I do have a toggle switch to be able to cut off the power to train horn.