RFI in coach electronics

[W4OHX]

I have a Yaesu FT-100D in the coach mounted at the drivers console feeding directly into a LDG tuner running RG8X to a hamstick mounted on the rear ladder. I ran a ground wire to the ladder from the frame of the MH. My problem is when I transmit on HF, there is some RF getting into the electronics of the coach, the entry step relay chatters, the inverter starts cycling on and off, the air bleed solenoid cycles on and off, etc. I put ferrite rings on the power cord, the feedline at both ends with no improvement. It all stops if I decrease the power output to around 10 watts or so. The lower bands, 40-80 seem to be worse. The rig is grounded directly to the frame as well. Any ideas ????? The coach is a 2004 Monaco Camelot with Cummins ISC 350.

Thanks,
Roger