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Old 12-01-2000, 11:08 AM
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Join Date: Feb 2000
Location: Germantown, MD
Posts: 106
85 300TDT 270k:

When the fuel guage gets down to the reserve mark the needle suddenly jumps to the full mark. What causes this? Relay somewhere? Solution?

On a different note...the ignition switch is getting loose and I wonder if anyone has experienced this. Is it necessary to replace the entire switch?

Thanks for your time,
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Old 12-01-2000, 01:06 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
More likely than not the problem is the sending unit. The sensor is a varible resistor with a very small range. From 5 ohms to 80 ohms. It's under the first aid compartment!(sedan) Very large socket!! OOPS!!! you said wagon. The floor covering in the rear floor must be removed to get to sending unit.

[Edited by M.B.DOC on 12-01-2000 at 01:09 PM]
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Old 12-01-2000, 02:26 PM
Q Q is offline
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Join Date: Aug 2000
Posts: 839
My 85 380Se does this too, only not as extreme. Mine is really inaccurate from about 1/2 to a little less than 1/4. The light is run from a seperate switch on the end of the sending unit, and it never faulters.
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Old 12-01-2000, 11:46 PM
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Join Date: Sep 1999
Location: Cremona, Alta, Canada
Posts: 263
Sounds like your sender. They can be taken apart (very carefully) and cleaned. Had mine start to jump around. Took it out and cleaned all the black crud of all the nice little wires and contacts and it works like a charm now. Just be careful with the wires, they are very fine.
82 300SD 110k
91 Caprice SS
92 Jetta TD
97 Cadillac Concours(300hp)
84 Celebrity 4.3L diesel
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Old 12-02-2000, 08:59 AM
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Join Date: May 2000
Posts: 317
Does this also apply to a 86 300E?
1986 300E
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