[DML] Fuel Sender or the Gauge?

["Steelwings" <steelwings@xxxxxxxxxxx>]

I'm having a problem with either my fuel sender or the gauge. I was hoping someone on the list might give me the benefit of their experience with this as I can find almost nothing in the archives. Here's what is happening: I have a stock, 1981 original gauge and sender. My tank is about half-full. The fuel gauge is indicating an "above full" reading with the low fuel warning light dimly lit. (The needle is at the 12:00 o'clock position) If I remove the sender and allow the float inside to fall to the bottom of the tube, the needle will drop to the "empty" mark and the fuel warning light will illuminate normally. If I manually bring the float up approximately 1/4 of its total travel up from bottom, the gauge will read "Full" and any linear increment below that point will deflect the needle accordingly.(for instance: 1/8 of the total travel from the bottom reads "half-full") I have removed the sender and examined it visually both inside and out. It appears to be in almost new condition. No visible damage, no varnish or discoloration of the plastic or metal components. The float and wipers travel freely along the "rheostat" winding. The windings appear to be evenly spaced and undamaged. I placed a VOM across the wiper lead and winding lead. At the bottom float position, it reads about 20ohms. At the top float position, it reads about 100ohms. Sliding the wiper along the winding , the readings are linear. Then, in circuit, I took a voltage reading across the leads. Black (ground) to Red (Power) was approximately 12.5VDC. Then I checked across black to yellow (the return) and I got the following: With the needle on the gauge reading "full" (4/4ths) with the float approximately 1/4 up from the bottom of the tube, I read 6vdc. (That is: 6 volts to cause the deflection to read exactly full) at 1/8th the travel from the bottom, 3 volts and so on. If I go beyond quarter of the way up from the bottom, the voltage exceeds the 6 volts and the needle will deflect beyond the full mark and continue counter clockwise until it can't go any further. All the way up (full travel) was about 10vdc.  The circuit looks pretty simple but the books don't give me any reference measurements to compare. Has anyone ever measured the resistance of the travel in the stock DMC sender? How many volts will cause a full deflection in the gauge? Any Ideas? Is it the gauge or the sender? Thanks in advance for any advice you guys might have.
Sal


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