Is the reserve light on the fuel level system in the 240d, 300d etc
independant of the gage level pointer?

When my fuel gage is at or below the last hatch mark, the reserve light doesn't come on. When I fill up I can only fill up to about 2 gals of listed capacity. So, what I am thinking is that the gage and the reserve are not connected. what says the learned members of the group??

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71 220D 169K wrecked
83 240D 118K sweet 4 speed
91 350SDL (one of the 60% good engines) 156K
84 300d (loaner to my sister) 189K
79 300SD (partswagen)
86 420SEL partswagen
70 220d (partswagen)
68 280s GASSER!!! under construction now
85 300sd 310K miles winter beater car retired
93 300d 2.5 turbo 168K wife's car
83 280SL euro 5 speed 155K
69 250S newest project 54K