Both SW fuel senders Bad

[Cfrisella]

Just a possibility.... I finished the 7a a month ago and have experienced fluctuations with both fuel senders. After going through the system, looking for bad grounds and connects ,I finally decided to just replace both. So far the problem is solved. Now.. the wings were finished four plus years ago and most of that time they were stored in the wing racks. I'm thinking temperature changes with summer and gravity slightly change the plastic components ever so slightly over time. Just something to consider. Plastic dries out and another possibility is the senders benefit from a fuel filled environment. Time will tell.

[hgerhardt]

Those fuel senders consist of a resistance wire coil with a metallic "brush" sliding over the coil to act as a variable resistor. The sender is not sealed and in fact fills with fuel. Since it's not sealed, the resistance wire will oxidize a bit if it's not stored submerged in fuel, leading to erratic readings. My -6 did that for the first few dozen hours until the oxidation got worn off from the brush sliding over the coil and it's been fine since. As did my '66 GTO which had a dry fuel tank during its 9-year restoration and had erratic readings too for the first few hours. Yours would have straightened themselves out after a while.

[Cfrisella]

That makes for good reason. Probably should have waited but I just want all to work correctly now.

[rvbuilder2002]

Originally Posted by hgerhardt

Those fuel senders consist of a resistance wire coil with a metallic "brush" sliding over the coil to act as a variable resistor. The sender is not sealed and in fact fills with fuel. Since it's not sealed, the resistance wire will oxidize a bit if it's not stored submerged in fuel, leading to erratic readings. My -6 did that for the first few dozen hours until the oxidation got worn off from the brush sliding over the coil and it's been fine since. As did my '66 GTO which had a dry fuel tank during its 9-year restoration and had erratic readings too for the first few hours. Yours would have straightened themselves out after a while.

Vans has not sold a wire wound style fuel level sender for many years. The senders that replaced them have carbon film resistors. That's not to say that something couldn't still happen to it because of long term storage, but I have never heard of any.

[gasman]

Originally Posted by rvbuilder2002

Vans has not sold a wire wound style fuel level sender for many years. The senders that replaced them have carbon film resistors. That's not to say that something couldn't still happen to it because of long term storage, but I have never heard of any.

Called Thick film on the box.