After months of studying and experimenting with sender units, I've come to realize design number 2 is the simplest, very accurate and will be the longest lasting. I've cleaned up and improved a thing or two and I have a bit more work to do, but it remains basically the same as you see below. There are also two added bonuses: the resistance coil (unlike any other sender) can be reversed for longer life if needed and this unit can be added to existing "aftermarket" sender hardware.
For over two months I've been working on a completely vertical sender which I had hoped would be the answer. While it is indeed unique, nothing so far has convinced me it will stand the test of time. I've also worked on pressure type electronic senders...in short, gravity plus the weight of the fuel in the tank will cause downward pressure which in turn will cause the sensor to output varying degrees of resistance. While this approach is interesting it is quite expensive and nothing at all tells me the sensors will stand up to ethanol for more than a year or two. And the most limiting aspect is the sensors would have to be specially made to output 0 to 30 ohms. No "off the shelf" part will even come close and some are backwards...meaning your gauge would register full when empty and empty when full. And finally I've looked into sensors which will measure the distance from the top of the tank to the fuel and send that as a varying signal. Those are very interesting and appealing (and accurate) but economically way out of the question. Anyone who knows me understands I enjoy solving problems, but at a point Occam's Razor dictates the proper answer.
The one I dubbed "new design"...being the one which converts the old arched style coil into a flat coil is simply better from the standpoints that matter. I haven't decided whether to make these for sale yet. I need to find a better source of wavy washers (some are ordered) and I need a way to compensate for wear so that at least 40 years of service from this unit. More will follow on this as time passes and some of the senders I worked on during the last 4 or 5 months will probably show up in the "for sale" section of the forum.
Last edited by Jon G; 03/18/20215:04 PM.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Hi Steve, If you hark back to the first post about the sender project, you'll see the original senders were encased in very poor quality pot metal which wore out rapidly. In addition to this, those senders had only one pivot and the rapid wear allowed the float rod/wiper to flop both back and forth and sideways. This first caused erratic readings (which in turn caused all the problems you'd expect) and later of course caused complete failure...failure coming from the pot metal (which invariably wore in an egg-shaped manner) and a poor design. I re-sleeved one with brass and ran a shaft for the wiper through that sleeved part and across to the other side giving 2 stable pivot points and that will help greatly, but I suspect most of the original senders have been discarded in favor of the aftermarket senders. It should be added the original senders were not serviceable. The aftermarket replacement senders are all made in either China or Taiwan. While Taiwan is capable of much better work none of that fine work was done on these senders they're making and I'm not convinced China cares much about the quality of anything they export. At any rate those after-market senders are either not going to work accurately right out of the box or they'll last about a year or two maybe. All but one of them uses the upturned arc coil (which while it can be made to work is a fundamentally flawed design but cheaper to make). If I make any replacement part for the AD trucks it is going to last for at least 40 years. Hopefully this helps explain things...in fact this answer sort of covers the spirit of the whole project. Hope all is well in Australia. We're enjoying "City Homicide," by the way. Well-written and well-acted series.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
