Ok so I finally finished it and it works. It didn't actually take that long, I just never had much time to dedicate to it.

I guess we need a brief history of what I was trying to do. I ordered the autometer quad gauges and the gauges are only set up for a fuel sending unit that they provide ( which won't fit without a decent amount of tinkering and gas tank removal) which operates in the 33(full)-240(empty) ohm range. Needless to say this will not work with our stock sending units which operate in the 0(empty)-90(full) range. So, using a fairly simple opamp circuit I was able to make it work with the existing fuel sending unit. The result is a box that you can plug inline with the sender and new gauges that corrects the voltage readings for the new gauge.






Here is a schematic of the circuit in question.




The little sub-circuit in the bottom left is the pre-existing gauge circuit that you tap off of.

First off, this was not very cost effective for me, however if there is anyone else out there trying the same thing it will cost you less than it cost me. The final design cost about 70 in parts(including the printed circuit board). You could do it for a little less if you built your own circuit board or use one of those universal kits at radioshack. However, I opted to save myself some headaches and have the board built for me by an outside company for about 33 (if you order at least 5 you can get that price down to 25 each).

If anyone finds themselves in a similar situation I can post part numbers and links. Anyone that can do a decent soldering job could do this themselves.

 

I keep watching this thread and I don’t know if it’s my curiosity or what. But I want to be the first to say . . . Nice work!

You have that figure it out bug. . . like me!

I find myself doing hours of tinkering taking things apart, putting them back together, taking them apart and well just looking for a better mouse trap!

I think what intrigues me more about this is why on earth they would make a dash unit that goes completely against the grain of the standard. . . Then I found myself trying to figure out a different way round it. Then. . .Well I had to let it go! You did it and I think it’s great!

Willcox Inc.

 

Awesome! yeah, I have that bug too. part numbers would be great.

I'll be 1 out of 5 for a printed circuit board. it would be fun to wire up my own surf board, but I like the professional look of a printed one (just knowing its there, even tho you cant see it).