hi

I need your help with a detailed wiring of my dashboard.

I am particularly interested in fuel gauge section (see attached).

The only wiring I've found in Haynes is only a block wiring.

Thank you.

Today I've took the dash out.

Here is the missing information:

R=10 ohms

V_reg=8.0 Volts

Now it begins the fun part: building a digital fuel gauge with 0.1 liter precision and able to follow the irregular shape of the fuel tank. I'm thinking of using a PIC microcontroller with the possibility of entering 10-12 reference points.

If you have better ideas, or full schematics, please share.

I don't think you'll get 0.1 litre precision from the standard sender, even if you parked it on totally level ground and left it parked for 10 minutes to stop swilling about. You'll need a lot of integral on your setup to do it, anyway, otherwise it'll be up and down like the stock market. There are plenty of setups people have done already with arduinos to do it, and it should work well once you've done it, but I think litre accuracy would be as much as you'd get, and I say that as a time served instrumentation engineer back in the day!

I could install a differential pressure sensor on the bottom of the tank and then the fuel slosh will never bother me.

and I say that as an avionics engineer back in the time when there were such jobs available.

here are some interesting findings for those fiddling with fuel sender - fuel gauge.

fuel gauge - sender circuit is powered from a regulated power source of 8 Volts.

fuel sender has a value of 435 ohms.

measured resistance between cursor and ground:

• 10 ohms for full tank
  
• 425 ohms for empty.tank
  

these values translate to a voltage excursion between 7.6V (empty) and 0.25V (full)

the fuel gauge has a heavy dampening effect.to minimize fuel sloshing.

the low fuel lamp comes on at around 10% of tank capacity.

when key on and low on fuel, the lamp goes on after 35 seconds.

Edited 5 June, 201214 yr by masster

more comments about fuel sender precision.

the resistance of sender itself is made of Nichrome wire and has some 90 turns, meaning 90 points the cursor makes contact on.

on a roughly 45 liter tank, this translates to a step of 0.5 liters for each coil turn :( bummer.

so forget about the sloshing effect, the sender itself is a mess precision-wise.