Lionel 6-17202 Railsounds boxcar horn problem

Seems like I have some railsounds issues lately.  I have a diesel boxcar that works fine for 5 mins and then the horn sounds and won't stop until you power it down and let it sit for a few hours. It's a Santa Fe 6-17202 Diesel. I think it could be a bad capacitor,  voltage regulator or cold solder joint.  I'm not an electronic engineer so I'm just guessing.  Any ideas? Seems like the regulator or solder joint could be effected by heat. Caps could be bad after 35 years.