if you need a relay to tie the coach batteries to the chassis/engine battery circuit, i highly recommend a BLUESEA
Automatic Mag Latch they're not cheap but the control you get is phenomenal.
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Don R.
'04 Haulmark (M42386) 42', 2 slide, 10kw -
Pictures
'04 F350 CrewCab Longbed 4x4, 50g aux tank & gear vendors dbl over