I have 2 control boxes in the trunk on the right side what are they for? I had noticed they are both disconnected

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'85 F250 6.9L diesel 2wd XL XC LB Centurion, Gone
'95 Mercedes E 300 Diesel W124.131 with a OM606.910 and just over 200k on the clock, needs top end engine work and a transmission.
2000 S500 W220 with a 5.0L V8 gas power.