in my e350, i was driving home last night and noticed that the WIF light was glowing dimly. in the past its never done this, it started popping on once, i drained the water seperator, and that solved it.
last night i tried draining the water seperator while driving, with no change. when i got home, i turned it off and tried draining it again, still no change. the weird thing i noticed with all this is that when the engine is idling, the light is off, but as soon as i give it any pedal, the light glows. so it appears to be somehow related to fuel flow.
has anyone ever seen this problem before? what should i do about it? the light is dim enough that i can only see it at night, and even then its not really annoying, but i don't want to keep going if this indicates a real problem i need to deal with.

 

I dont know so much about fuel flow, but perhaps alternator current, not sure how the things work but maybe the ground is goin. My blinkers do this occaisionally, (sockets backfeeding somehow). You wont see it but as soon as you give it any throttle (alt goes from roughly 12.4 to 13.8) the blinker lights up really dim.

No idea if the same principle crosses over, but was the only thing to come to mind. My WIF sensor must be toast, ive never seen it come on, maybe never had water in it, so curiousity got the better of me and i actually put water in it pre filter change and it did nothing. Which leads to my next point. If you cant get it fixed, disconnect it and get in the habit of draining the bottom off every fill up or once a week or so. If you go to the same place all the time for fuel and they typically have good quality you might not have to worry about it, i never do.

 

i know mine works cause it actually came on once, it would flash on now and then as i was either accelerating or decelerating, i don't remember which, but was obviously just at the point where the sensor kicked in. i learned how to drain it at that time.
as for fuel, i always use one station where all the local truckers go, and never had a problem, only had the sensor pop up once in over a year and 40k miles

i'll look into grounding issues next time i see the light glowing

 

I had that happen a few times last winter when it was damn cold out (at least for my area, probably like normal Canada weather for winter...)
Drained it and not even a drop of water... Warmed up the week after and no issues since. Not sure what the hell happened, but possibly ground issues somewhere. My tach doesn't work either and I think its related to a ground issue, but haven't had the time to care about it.

 

it hasn't been cold here, approaching freezing at home, highs somewhere in the upper 40s in various places i've been, so it looks like you've been on my same path with no answers... thats a good enough excuse to pour both of us a good brew