fuel light

Post by **Vart** » 29 Jul 2005 11:09 pm

do these have a tendancy to go a bit weird? my DL's one comes on practically at the mark before empty (quarter) where as in the nasty cold it will happily reach just before empty before it comes on.

does the light work from a sender or from something else and are they hard to replace?

Post by **petavius** » 30 Jul 2005 12:09 pm

Id like to know about that too, mine comes on at about 3/4 full and stays on so I never know what my fuel level is?!

Post by **5lab** » 30 Jul 2005 12:51 pm

the light is more likely to be accurate than the gauge - so if the light comes on first or after its likely that the gauge is a bit dodge

Post by **Duvel78** » 30 Jul 2005 02:39 pm

petavius wrote:Id like to know about that too, mine comes on at about 3/4 full and stays on so I never know what my fuel level is?!

I had a similar problem, it's not a problem with the gauge; the sender in the fuel tank was broken... Easy to change!

Post by **Vart** » 30 Jul 2005 06:32 pm

can ones from a 1.7 be put into a 1.4? i see they have the same tank capacity.....

is the line before empty 1/4 or the start of the red?

Post by **jtbo** » 30 Jul 2005 08:04 pm

My fuel gauge measures only last 10 litres nowdays, led has never got lit as fuel is out before 2nd mark from left, needle also stays full position until there is that 10 litres left, then it quite quickly comes near to 2nd mark as 10 litres is about 100km.

Need to change that sender in tank, does it come complete or it is needed to attach to old part that has hose connections?

Post by **morgan105** » 31 Jul 2005 01:00 am

I'm not sure wether it's right or wrong when coming on around the 1/4 mark because my dad's does the same but I haven't bothered to check it out yet because at least it gives you a good warning that fuel is starting to get low.

One thing to check first before tank and sender removal is the voltage stabalizer which is on the rear of the instrument panel (rectangular plug in, like a long relay). Take this off and connect a voltmeter between I and E terminals of the stabalizer, the voltage should oscillate between 0 and 5 volts. If this is not the case then the stabalizer is faulty and must be renewed.

If it checks out ok then it's time to check the tank sender, if alright then you need to check the wiring from sender to gauge. If still all ok then it's time to replace the gauge.

morgan105

Post by **foggyjames** » 01 Aug 2005 02:09 am

How does measuring the voltage across the (disconnected, right?) stabiliser work? Unless it has some capacitance, it'll tell you nothing, and even then only for a few moments (depending on the amount of charge). Or did you mean resistance? I'm confused...

Mine still works AOK, with the light coming on almost exactly as you hit the reserve. Good to know people are on top of this in case it ever goes AWOL.

cheers

James

Post by **redline** » 01 Aug 2005 09:16 am

mines the same as Foggys i.e. perfect LOL

Post by **bodejodel** » 01 Aug 2005 09:22 am

Same here, the gauge gently drops from full to empty and the light goes on when there is about 10L left in the tank...

I guess when you pamper the car like we do, you get something in return... no faults at all...

Post by **morgan105** » 01 Aug 2005 11:21 am

All the stabalizer is doing is checking the voltage coming in to the system then based on it's value checks for errors and corrects it to maintain a steady output voltage to prevent load damage. It checks it about 6-12 times a second for under or over voltage then brings it back to nominal values.
It's just a regulator so it can be checked while disconnected.

This also works the temperature gauge along with the fuel gauge.

morgan105

Post by **foggyjames** » 01 Aug 2005 12:43 pm

I'm afraid you're heading on the wrong path here...that simply isn't how voltage regulators work. They adjust an 'incorrect' input voltage (either high or low) to a set output value - very clever. However they do it continuously, and they can't generate a voltage themselves - ie: like a battery. If you want to measure one, you need to measure it 'in action' - hook it up, fire it up, and measure the voltage on the output pin.

cheers

James

Website · Post by **antiekeradio** » 01 Aug 2005 01:57 pm

james, these car regulators are antique, compared to modern day solid state examples.

they switch the full voltage on/off and the ratio between on and off time determines the position of the gauges. this works because the gauges are pretty slow...

Greetings Wouter

Post by **Chris_C** » 01 Aug 2005 02:00 pm

Foggy's right on this, the voltage regulator is a completly analogue component, so is completly in the continous domain. The way in which most multimeters work (note most) won't pick up any signal with the component disconected, and even if a signal was seen, most would be too slow to interept the oscillations (again, most, some good analogue meters would see it) What I can't get my head round yet is what this reading would relate too, it wouldn't be true voltage as voltage cannot exist without current, current cannot exist without a source. No source is inbuilt to a regulator, so the reading would show transient changes in resistance (highly unlikely most affecting variables will be stable). This would also be completely device specific, as no calibration for this can take place.

I am intrested in this however, and wonder if you can explain how this test works Morgan? As far as I am aware, the regulator in the 300 dashboard isn't one that contains any error correction as you say. From recolection its a standard three pin device that just provides a steady 12V from the less than stable car sources (battery and alternator). This is to protect the logic circuitry used in the gauges from spikes.

Edit having seen Wouters post:

I'm sure that they are still a fully analogue component Wouter, and are most definately solid state, the component in question is the single 3 legged device mounted in a socket on the flexable green plastic, not mounted to any of the gauges.

Website · Post by **antiekeradio** » 01 Aug 2005 02:10 pm

could be that the newer dashes have a solid state (silicon, transistor like) voltage stabiliser. i'm 100% sure the 343 has a mechanical (like blinker relay) stabiliser, that switches on/off by heating wires etc..

however it works, it has nothing to do with the 'almost empty' light.

if that comes on too early, there's something wrong inside the tank.