Fuel Level Indicators

[Massimo]

Ok another teething problem. My fuel level indicators are not showing the correct fuel level. As soon as i switch the power on, the needles go to the full position and stay there. The indicators are brand new VDO. The fuel level senders in the wings are . . . i dont know So some folks are talking about earthing, others about different ohms between sender and indicator and so forth. I have not as yet opened up the sender as this means removing some rivets and i want to try and delete all other options before taking this route. Any body got any other ideas?

[Morph]

Fuel level sensors are usually resistive, i.e. they have a float that moves up and down and this then moves a contact along a winding of resistive wire. The one side of the wire is connected to earth. The concept is the float moves the contact up and down along the wire windings, adding more or less windings and as a result increasing or decreasing the resistance.

This mechanism requires minute amounts of current and voltage and as such will not ignite the fuel.

Now the first test is to see if you are getting varying resistances. Get a Fluke multimeter, and connect it between point A and earth. (disconnect the VDO unit at this time)
Start with an empty tank. add fuel to the tank and measure the resistance. Try and get the minimum and maximum readings in ohms.

If you get no readings, then the earth wire is missing from the flange of the tank to the earth or the wire from the center point to point A is not connected.
If you get a fixed reading then the float is stuck and not moving
if you get variations of ohms, check your gauge to see what it is expecting. You might have a high resistance sender with a low resistance gauge or if the tank is not a standard shape the variation in resistance from full to empty is too small.

The MGL gauges allow you to calibrate your sender and gauge to handle any shape of tank. There is an empty, full and 4 or 5 other points. You add say 20 liters of fuel, get the reading off the sender, then tell the gauge that this is 20 liters as an example. The electrical gauges don't give you the option to calibrate

[Massimo]

Geez Morph, how you possible got to know all this stuff is amazing. I will test it over the weekend. Thanks

[Morph]

Been there, done that, installed various versions in different tanks

[Massimo]

Uhmm what is a "Fluke" multimeter?

[Morph]

Available from any good builders warehouse, hardware store

measures, AC/DC Voltage, resistance/continuity, capacitance, current, and temperature (lekker for testing your CHT probes and stuff)

About R180 will get you a nice one. Good to have in the home

[Boet]

Jaaa, he`s not just a purtty face he is, our Morphman!!

[ystervark7]

A multi meter you will get for R200, a Fluke multi meter like the one in the picture will be closer to 10 times the price. Any multimeter should do the job, just do not press the radio's PTT while you are trying to measure anything...

[Duck Rogers]

It was just a fluke you managed to find a pic..

[Morph]

It was just a fluke you managed to find a pic..

[Oupa-G]

Massimo before you continue first check if your arm that rotates has a good connection between the arm and the rest of the connection because the current flows with very feeble spring washers which are prone to poor contact I had the problem with my Vansin I solved the problem with a curled wire soldered on at both ends an suddenly I had fuel gauges that are accurate. The sliding connect runs in fuel and normally has a long life , also check that your float is a float and not a sink . I have also had that on my Baron and that was a so-called certified part. Just some information.


Cheers Oupa-G

[Morph]

A multi meter you will get for R200, a Fluke multi meter like the one in the picture will be closer to 10 times the price. Any multimeter should do the job, just do not press the radio's PTT while you are trying to measure anything...

Seeing as we are being overly pedantic

here is the "Fluke" that will do everything for you at about R180

Apologies to the experts

Major Tech, as good cheaper version of the fluke

[Grumpy]

Does it come with a Corsa stand too?