AUX fuel gauge

[evangelos]

hello all,

i am having problems my fuel gauge. it seems to have a mind of its own. i was told its the consol and i am looking for a simpler solution ; would a standard autometer fuel gauge work?

if not what other brand would work and/or what specs would the  gauge have to be.

thanks

[Black Smokin' Diesel]

What do you mean by "mind of its own"? I know that the fuel moving around in my tank makes the gauge act up a bit (more fuel on left turns, less on right turns...).

[evangelos]

ok, what i mean is that it will indicate 1/2 empty and instantly drop by 1/8th then as the rpm's climb it will pass the 1/2 and then come down again. it has been doing this often lately.

the temp gauge is not jumpy because it was mentioned that this is a defect of the console on the mk3's ; but if it is i will not go through the hassle of looking for a console.

i just won an auction of a fuel tank for my veg configuration and it happened to come with a fuel gauge and i wanted to use it.

thanks for the interest.

evan

[mk2diesel]

sounds like the voltage regulator on the back of the panel is fried ( altenator voltage goes up as the engine speed increases from idle ) fluctuating voltages causes the fuel guage to be eratic ...as well as most of the other guages ....  its a small black unit with 3 wires sticking out of it ... and screwed to the back of the guages ( usually speedo)  ... the 3 small wires clip into the foil on the back of the guages ...

[evangelos]

thanks mk2diesel,

is that piece sold seperatly?

does it effect the alternator voltage regulator?

thanks

[rubadubdub]

as i understand it the voltage stabiliser on the dash clocks takes the power from the main battery system and stabilises it at 10v which suits the instruments. You can check its working with a multimeter.

UNscrew dashboard and remove clocks but dont unplug the multiplug. The voltage stabiliser is a square chip with three prongs coming out that slot into the circuit board. THe three prongs carry live from battery, earth and live to dash clocks (but i cant remember which is which, its in Bentley). With your multimeter measure between two of the prongs, between earth and battery you should get ~12v, between dash live and earth you should get ~10v. If you dont that could be whats making the fuel gauge play up.

Because the guage is going up and down when you put your foot down it may be the voltage regulator on the alternator, as no matter what speed the regulator should keep it at ~12V (but more than 13v when charging).

Before you take your dashboard apart quickly test the charge to the battery is constant as if this is wandering up and down when you put your foot down this may be the problem. You'd probably have lights dimming and getting brighter too if thats the case.

[evangelos]

hey rubadubdub,

the fuel gauge dial does not consistantly increase or decrease. the headlights do not dim when the rpm's drop.

is there a spot on the alternator i need to make contact with my multimeter or do i simply touch the positive and negative ends on the battery. sorry for the newbie question.

thanks

evan

[rubadubdub]

The way i did it was to test across the battery terminals. When the car is not running it should read ~12v. Start the car but dont press the accelerator (ie battery light still on) and it should stay around 12V.

Press accelerator a bit (or pull on pump accelerator cable arm so you can do it without a friend) and battery light should go out and the multimeter should jump to about 13-13.5 ish. It will hover about slightly but even when you drop the revs it should stay above ~13v.

Put all the lights, stereo, rear demister, fog lights and heater on and check it still reads 13v. It will drop slightly but if it goes much below 13-12.5v it means your alternator isnt charging.

Ive never had that voltage regulator go wrong so cant advise what it will happen if it does (anyone else?) but common sense suggests the voltage generated by the alternator will wander up and down.

Hope that helps.