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The fuel gauge on my 2.0i Sport Frontera (1998) has packed up - problem is, which end do I start looking?! The tank (sender) end or the dash end? I have checked all of the relevant fuses, and all are OK. Can anyone offer me any advice? Thanks in advance!
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Pull the wire off the sender on the engine. Ground the wire on the block. If the gauge shoots to 'fully hot' then the gauge is OK (don't hold it there for long). If not, then you have a gauge or wiring problem.
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Doesn't the temperature gauge generally play up as well if the fuel gauge itself is at fault?
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Dynamic Dave - you may (but just MAY) have a point in that the temperature gauge has been showing "low" results recently - I had put that down to one of 2 reasons; 1. The temperatures where I live (in the Alps) have dropped significantly recently, aand/or 2. The thermostat needs to be changed.
It worries me a little to try to ground the sender against the engine block - it seems to me that I may, in fact, cause a failure of the gauge, even if there isn't currently one!
By the way, I have to tell you (all) that despite the fact that this is only the 3rd time I have used this site, the responses and advice that are given by "Joe Public" (albeit the experienced version of the species) and the professionals alike are priceless. I think that you (Mr. Webmaster) should charge for access to this forum. Friendsreunited.com charge £5 for a year for something which is in effect useless. If you were to do the same, I'm sure that the 200 posts that you have counted today would be of even greater quality.....
Regards
Richard ROGERS
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IIRC if the fuel sender is not working.it should not affect the temp guage..That may be a seperate issue.Possibly the thermostat.I dont know the Frontera so may be wrong?..But would not worry about directly earthing the connection.As Aprilia said only hold it there to check guage works
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Steve
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Sorry, my post (above) looks a bit odd - I misread it as temp. gauge - not fuel gauge. Sorry. Advice is the same though - briefly ground the sender end of the wire.
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temperature gauge has been showing "low" results recently
Then it cold be the voltage regulator on the back of the instument binacal.
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Usually (pre multiplex wiring and electronics) the Temp and Fuel gauge were very simple instruments.
Basically they are both fed a regulated voltage on one side of the needle (from a regulator pack in the instrument binicle) and the other side is variably earthed to ground.
In the fuel gauge this is the in the tank, basically a float attached to a variable resitor.
With the temperature gauge this is a resistor in the engine block that varies by temperature.
So what we have is the current going through a wire wound round a bi metalic strip that bends and is attached to the needle.
Very crude, not very accurate, but very simple.
SO! given that both gauges are fed positive voltage from the same source, if both go up the pole its that source (usually the regulator pack)
If one goes up the pole its the "variable earthy bit" that is at fault. Grounding it to earth makes the gauge go to Full Scale Deflection - full of fuel or boiling hot. Using the grounding technique is a good quick check and aid to diagnose the problem.
The other bug bear is when the engine earth to body starts to break down, the engine starts to try and earth through other ways, one of which will be the wire to the temperature gauge causing it to go haywire.
All this goes to monkeys of course with clever modern electronics and multiplex wiring where you should never ground anything unless you know exactly what you are doing.
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(You see - as I said before, answers like that are worth a fiver a year - surely!?)
However, that now leaves me with the question - "is my 1998 Frontera a backward beast with variable resistors and bimetalic strips or a clever car with multiplex wiring?" I am told that the engine is the same as the old 2 litre 8 valve cavaliers and older Vectras...should I take heart from that or panic?
Thanks!
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Almost certainly non mulitplex wired. They may have done some half hearted fancy electronic gimics with the instrument pack, but the actual variable thingy parts will be working the same way, so as long as you identify the right wire, grounding should work.
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OK - the gauge works - I can make the oil pressure, temp and fuel gauges go off the scale (!). I guess it's at the tank end. Is it likely that I'll have to drop the tank out to change the float????
Thanks in advance.
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Should be a an inspection cover in the body floor above the tank where the sender goes in. probably covered with a rubber or plastic bung, under the seats maybe?
The whole float/sender assembly comes out through this inspection hole.
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Not sure about the Frontera but from experience on Cavaliers the sender sits at the front side of the tank facing the engine under a round plate (the sender wires pull off this plate) which is easy to access with the tank in place, although the fuel level needs to be quite low. This is even though there is a rubber inspection plate/bung under the rear seat as Renault Family says. I assume this is for a fancy GSi or 4x4 tank. I expect you will need a new seal as well as the sender unit.
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Not sure about the Frontera but from experience on Cavaliers the sender sits at the front side of the tank facing the engine under a round plate
Victorbox,
on later Cavalier's they moved the sender unit to the top of the tank, so it could be accessed through the rubber bung under the rear seat. My J reg (91) one was on the side, as you say, but my L reg (93) was on top.
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"OK - the gauge works - I can make the oil pressure, temp and fuel gauges go off the scale (!). I guess it's at the tank end. Is it likely that I'll have to drop the tank out to change the float????"
I do hope you mean individually and not all at one with one wire!!!!
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No - just my random fashion of trying pretty much anything I could find happened to mean that the last one I tried made the fuel gauge jump. Interestingly, the low-fuel warning light came on too!
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They are doing something fancy in the instrument pack then. There is some small electronic gizmo saying "aha the sender is saying really really empty so i will turn this light on then"
Interesting tho, that the sender is duff enough not to move the gauge but not duff enough to bring the light on.
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(You see - as I said before, answers like that are worth a fiver a year - surely!?) However, that now leaves me with the question - "is my 1998 Frontera a backward beast with variable resistors and bimetalic strips or a clever car with multiplex wiring?" I am told that the engine is the same as the old 2 litre 8 valve cavaliers and older Vectras...should I take heart from that or panic? Thanks!
Frontera doesn't using bimetallic strip gauges, it uses what is known as a 'moving iron' unit. They are pretty robust. The low fuel warning light is operated by a semiconductor comparator (an 8-pin IC) which compares the signal from the sender with a reference voltage level. If signal is below reference then light comes on.
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Assume then that the earth does not go direct to the instrument as they would need something to damp down the tank float fluctuations.
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IIRC the movements on these are filled with silicone fluid to provide damping. Lots of gauges are of this type now, I think the old bimetallic strip type have been obsolete for quite a few years, presumably because there were not accurate enough. Latest ones (and most Japanese) use a 'cross coil' movement which is driven from a microprocessor - obviously a lot more complex.
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