I am looking at the OEM manual and it's testing proceedure is not very clear. I have a dual tank system and I have narrowed down the problem to either the gauge itself or the wiring to the gauge.
How do I test the gauge itself once OFF the car? There are three prongs on the gauge two on top and one on the bottom one is fed from the tanks one ign and one ground. Does anyone know which is which? Also I have tried tracing the route of that wiring face behind the instrument cluster does anyone know how this thing works?
It's a potentiometer if I'm not mistaken. The prong in the middle should connect to BOTH the connectors on either side. It goes like this 1 80% 2 20%
3 or if you change it 1 40% 2 60% 3, ie - it's a smooth wiper action. You can test it by attaching a lead from an ohm meter to the middle of the pot, then one to the other side. It with it should measure something in the hundreds of ohms. If it doesn't have any resistance it's dead, if it has infinite resistance it's dead, or if the resistance curve isn't smooth it's dead.
I'm not really following you on the 1 80% 2 20% 3 thing, but here is what I got: looking at the back of the gauge: L R M L = Left prong R= Right prong M = Middle prong (bottom)
Setting my Ohm meter to 20K, I get the following results when I connect the leads: M to L = .09 M to R = .13 L to R = .04
The M to L = .09 and L to R = .04 equals the M to R = .13 So I see a pattern and from your description it would seem that this gauge is good, Is this correct?
You are mistaken, he's asking about the -dash gauge- itself, not the sending unit in the tank(s) which does somewhat resemble a potentiometer. The dash gauge more resembles a wheatstone bridge (or half of one), where there are two coils, one is fed 12 volts and the other fed a reduced voltage from the sending unit, the balance between the voltages acting on the coils is what causes the gauge needle to move
Off the vehicle; You'll have to physically trace down which gauge pin goes to what colored wire in the instrument cluster connector. (there's only 16 circuits into the cluster, so it shouldn't be too difficult) Pink/black = 12 volts Black = ground Pink = sending unit variable resistor
Once you have the pins identified, connect 12 volts and ground to the appropriate pins, connect a variable resistor (IIRC 30-90 ohms) to the appropriate pin, adjust the variable resistor thru it's range, the gauge should respond accordingly, low resistance = low gauge reading, high resistance = high gauge reading.
Do not allow the sending unit side of the circuit to go open circuit when 12 volts is applied to the other two pins.
On the vehicle; Ground the pink sending unit wire at any convienient place that it can be accessed, the gauge should read low (empty), with the ignition off, connect a 90 ohm resistor between the pink wire and ground, turn the key on, the gauge should read full. Again, do NOT open circuit the sending unit circuit (pink) when the ignition is switched on.
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