Using my horns with my remote & switch.

1994 Chevy C/K 1500 2dr, Recenlty installed 791xv, I wired in a polarity reversing relay to the (-)output of channel 4 to use with my train horns which are operated by a (+) electric solenoid valve. I can use the horns with my remote but I cant use the toggle switch in the cab. I am assuming I need a diode installed? I tapped the relay (+ outgoing) into the (+) wire for the valve. I believe the relay is picking up the voltage and grounding it out as everytime I use the toggle switch it burns the constant fused 12v source to the relay and toggle switch. I am a newb so please be kind and point me in the right direction. I have researched the information on relays and diodes but can't come to a conclusion on what to do. I did not install the alarm so if Im doing something completely wrong tell me to stop and I'll take it to the shop.

Thanks,

James

what wire is the toggle switch wired into assuming it is the 12volt wire to the horn u should ......from the 791xv u should have pin 85 negitive channel from brain.....86 12v constant.......30 horn side of the toggle switch (cut this wire).....87 12volt constant......and 87a (same wire u cut and used on pin 30) but use the other side of the wire that is goign back to the toggle switch.

Ok it is wired like this now  12v+ from battery to momentary rocker switch then from switch to valve to control the train horns, now when I installed the relay, I took and used this diagram

I then took and t tapped the 87 into the wire going to the valve. So maybe that should help.

*update*

I got it working by putting a diode in.