O/T: how to wire an aftermarket fuel sending unit and gauge
hey guys, this is a real common type aftermarket gauge and sending unit like what you would see for an auxillary fuel tank in a truck or for a boat. i lost the distructions so i don't know how it's wired. anyway, there's three posts on the back of the gauge, one is 'G', presumably for ground. the other two are 'I' and 'S' if i remember correctly.
i've done some searching on the web but haven't been able to come up with any instructions. what i'm thinking is 'G' is obviously ground so ground to there and the ground on the sending unit. then 12v switched into 'I' and from 'S' to the sending unit.
i just don't want to spark things up on a fuel tank if you get my drift.
Search on autometer.com and look through their fuel gauge directions. I wired mine to their recommendations and it works great. If I remember correctly I believe G is ground I is insturment panel (12V switched) and S is to the signal wire from the sending unit. Autometers are set up the exact same way with G S I terminals.
o.k. now i'm stuck. i wired it up like i thought it should work and nothing. well, correction, at about a 1/4 tank the needle would kind of bounce a little. i filled up the tank and it went completely to empty. so i checked the instructions for the VDO in the link i posted and it has the 'S' terminal going to the outside ring of the sending unit and the 'G' terminal to the inside post. that seems terribly odd to me as i would think for sure that the 'G' or ground as i assume would go to the outer ring that bolts firmly to the tank, and thus, is grounded.
does that make sense to anyone else?
On mine I used a sunpro to replace the original and the sending unit in the tank was riveted onto the filler neck. I had to cut it off very carefully and then bore the hole to match the new unit. You have to use the phonelic washer to make sure that the signal wire contacts don't short out to ground on the filler neck flange. Are you sure you measured the depth and angle of the sending unit arm to match where the original one was? Mine bounces around a little when driving but after a few seconds it settles down. I think the arm is a little too loose and moves around with the fuel, so it shows in the gauge readout. When I was handling it out of the tank I actually thought it was binding but then I thought about the fuel sloshing around and just installed it the way it was. The bouncing needle is a little annoying at first but I know it works good.
Oh and the gauge and unit have to be a matched pair, don't try two different brands together unless you what ohms they are rated to, like 0-33ohms or 266-33ohms. It's for reading empty to full and vise-versa or if you mix matched parts it might read empty when you fill up the tank and full when empty.