Ok someone must know why the reserve light is not testing.
The sending unit reserve light switch does not work . I tried to get it to work but it would not. But the test circuit is completely seperate to my knowledge.

What I do know.
The bulb is good.
The dash circuit from the bulb to the cable is good, pin 4 and 5
The resistor on the circuit/dash board is fine 17.7 ohms.
The diode on the circuit/dash board is fine correct in one direction.
The continuity from the lamp to the #7 pin ( #7 provides the ground) shows the normal resistance.
The test circuit power comes from pin 5 and shows normal voltage when the key is in run.
The ground for the test circuit goes out pin 7 which also ground the battery/charge light.
The battery charge light does come on with the key in run and goes out when the car is started.
The #7 pin goes to the alternator for its ground so I may have something wrong in the voltage regulator or alternator.
The charge light operates normally and the battery has not died due to lack of charge.
If I have a problem with the #7 pin wire to the alternator why is it comming on in "run " and going out when the car starts?
The #7 pin has a second wire that goes to the warning circuit for the brakes. It has diodes so it should not be the normal ground.

Tomorrow I will check the alternator and voltage regulator.
Otherwise I am completely stumped with the reserve light not testing

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car