Ouch, you've got some bare wires mixing it up somewhere. Time for some serious exploration of wire bundles and looms, pushing here and pulling there to see if you can determine where the short is. Problem could be under the dash, under the hood, or any place that 12VDC could run into your horn and brake wiring. Could be anywhere around the fuse blocks too which are also under the dash or hood. Could be an interesting problem for either you or Mr. Jayco to find.
2015 Greyhawk 29MV
Honda CRV toad with Blue Ox baseplate
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TST 507 Flowthru TPMS