blaze Posted January 8, 2008 Share Posted January 8, 2008 98 OBW, 200,000 miles. Low fuel light never worked since I bought this OBW in Nov 07. It doesn't come on when key is turned to the on (ACC) position? Also there is no bell or chime. Everything else seems to be fine, no blown fuzes. Maybe the previous owner only kept 2 gallons of gas in it, and blew the light Anyone else had this problem? How do you fix it? Is there a bell or chime besides a blown bulb? Quote Link to comment Share on other sites More sharing options...
hklaine Posted January 9, 2008 Share Posted January 9, 2008 ive got the same problem, i think. unfortunately no solution. i've put 13.x gallons in it, and have never seen the light. Quote Link to comment Share on other sites More sharing options...
njdrsubaru Posted January 9, 2008 Share Posted January 9, 2008 as far as i know the light is not supposed to come on unless you are really low in gas, something like 2 or 3 gallons... maybe the bulb in the dash is out? or the fuel level sender is bad check those out Quote Link to comment Share on other sites More sharing options...
hohieu Posted January 9, 2008 Share Posted January 9, 2008 Could be a dead bulb or a problem with the in-tank sensor or related circuits. I had the same issue and replaced the bulb, but the light still still fails to illuminate, even after I'd taken it down until over 15 gallons was needed to refill the tank. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 9, 2008 Share Posted January 9, 2008 YAY WERE BACK! you have a 15.9 gallon tank. Light doent come on till almost 14 gallons gone. Want to see the light, run it al the way down. Carry a jerry can just in case. nipper Quote Link to comment Share on other sites More sharing options...
Skip Posted January 9, 2008 Share Posted January 9, 2008 Howdy Blaze, sorry no bell no chime just a lame little light. If you do want to test / fix it... Behind the rear seat next to the pass side strut tower under the carpet is a cover in the floor. After removing the cover you will see the top of the fuel tank and the fuel pump and fuel level sender wiring. Here is the strange part. The light comes on when a sensor (called in the FSM a "thermistor" --> strange part see below) in the tank grounds the wire for the dash light. A "thermistor" is a thermal device that varies resistance as a function of temperature. In this case would vary the voltage across the lamp? http://en.wikipedia.org/wiki/Thermistor The wire from the plug you will see is a blue w/ green tracer wire. (Gen I Leg. info here) This wire runs to the lamp. The lamp is given positive battery voltage on it's other side. This all seen on the wiring diagram in the FSM. I have also read where the ECU needs the fuel temp so this devise may function as both. The ECU may ground the lamp at a certain voltage like when the sensor is exposed to air?? I tested the one in the picture and it did vary it's resistance with temp. How the lamp knows when to come on given a certain voltage as the thermistor would do is a good question. I'm sure this doesn't help much, it does bring up a very interesting question. I thank you for giving me a reason to investigate it. Quote Link to comment Share on other sites More sharing options...
EVOthis Posted January 9, 2008 Share Posted January 9, 2008 I was having the same problem...low fuel light didnt come on at all in ACC but i do believe i have seen it on before though....thank you so much for the info...the photo is very helpful also... Quote Link to comment Share on other sites More sharing options...
frag Posted January 9, 2008 Share Posted January 9, 2008 Don't presume the light is not working cause you dont see it with the other idiot lights when the ignition is at ON and the car has not yet started. That's how it works. Dont ask me why. You really have to drive your tank to the last few liters for it to come on. I tested it once, with a jerry can, and IIRC i was able to drive close to 70 kilometers (highway) before the engine began to stutter. Dont completely trust the gauge either. The needle often goes under the E mark without the low level light coming on. Quote Link to comment Share on other sites More sharing options...
gbianchi Posted January 10, 2008 Share Posted January 10, 2008 THIS BOARD ROCKS, with the knowledge and info tidbits found here and some manual dexderity and just a few GOOD tools we could fix any subee on the planet!!! Quote Link to comment Share on other sites More sharing options...
daehttub2000 Posted January 10, 2008 Share Posted January 10, 2008 This board and its members never fail to amaze and impress me with all the "do-it-yourself" help and advice--and it even comes with pictures:banana: Anyway, my 95 legacy's low fuel light doesn't come on until I have to put in about 13.5 to 14 gallons gallons into my tank. The LFL doesn't come on with the rest of the idiot lights when I turn the ignition on. The Subie also has a "reserve" amount of something over a gallon in the fuel system so I've actually put in 15 gallons before. You really have to run it down to see the light. Yes, I'm the knucklehead who drives around with the low fuel light on and I do have that little jug of emergency gas substitute in case I really push it. My friends have learned to keep an eye on my gas gauge on long road trips:rolleyes: Quote Link to comment Share on other sites More sharing options...
nipper Posted January 10, 2008 Share Posted January 10, 2008 This board and its members never fail to amaze and impress me with all the "do-it-yourself" help and advice--and it even comes with pictures:banana: Anyway, my 95 legacy's low fuel light doesn't come on until I have to put in about 13.5 to 14 gallons gallons into my tank. The LFL doesn't come on with the rest of the idiot lights when I turn the ignition on. The Subie also has a "reserve" amount of something over a gallon in the fuel system so I've actually put in 15 gallons before. You really have to run it down to see the light. Yes, I'm the knucklehead who drives around with the low fuel light on and I do have that little jug of emergency gas substitute in case I really push it. My friends have learned to keep an eye on my gas gauge on long road trips:rolleyes: You had plenty of gas. My largest fill up was 15.7 gallons oopsy nipper Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 10, 2008 Share Posted January 10, 2008 For those who would like to test the light operation I think you can do this by adding a resistor to the lead going to the thermistor in the tank and then touching the other end of the resistor to ground. This will bypass the thermistor and decrease the resistance to the light so it can turn on. I would guess the resistor value may need to be around 40 ohms as a safe value but it may require a slightly lesser value. A 1 watt resistor will be safe power also. The light isn't tied into the test circuit so it won't come as others do when the ignition is turned on. It will only turn on when the fuel gets low enough and allow the thermistor to turn it on. Quote Link to comment Share on other sites More sharing options...
forester2002s Posted January 13, 2008 Share Posted January 13, 2008 Here is a link to a 2006 thread on this subject: http://www.ultimatesubaru.org/forum/showpost.php?p=469698&postcount=20 Note the reference to a 10-minute delay (before the Low Fuel Lamp comes on). Not sure if this applies to all models. Quote Link to comment Share on other sites More sharing options...
Towel Rail Posted January 13, 2008 Share Posted January 13, 2008 IMO, by the time the light comes on, you should've filled up a LONG time ago. Quote Link to comment Share on other sites More sharing options...
blaze Posted January 13, 2008 Author Share Posted January 13, 2008 Ran it out of gas today. After reading a couple of threads about gas gauges being way off, I wanted to know how accurate mine was, along with fixing the low fuel light. I carried a gas can with me, and after reaching the Empty mark, then a hair lower, it bottomed out. Then went about 30 miles before it sucked air. Can't believe it went dry 10 feet from my garage door At least I didn't have to stand on the side of the road. After 30 years of driving this is the first time I ever ran out of gas even though it was intentional. Anyway the light did not come on? So maybe the bulb is blown or the unit in the gas tank is inop? :-\ Quote Link to comment Share on other sites More sharing options...
nipper Posted January 13, 2008 Share Posted January 13, 2008 Ran it out of gas today.After reading a couple of threads about gas gauges being way off, I wanted to know how accurate mine was, along with fixing the low fuel light. I carried a gas can with me, and after reaching the Empty mark, then a hair lower, it bottomed out. Then went about 30 miles before it sucked air. Can't believe it went dry 10 feet from my garage door At least I didn't have to stand on the side of the road. After 30 years of driving this is the first time I ever ran out of gas even though it was intentional. Anyway the light did not come on? So maybe the bulb is blown or the unit in the gas tank is inop? :-\ So not going to tell us the number Check the bulb, as the transducer is fairly trouble free. nipper Quote Link to comment Share on other sites More sharing options...
blaze Posted January 13, 2008 Author Share Posted January 13, 2008 So not going to tell us the number Check the bulb, as the transducer is fairly trouble free. nipper 14.8 gallons? Is this the number you looking for? Quote Link to comment Share on other sites More sharing options...
nipper Posted January 13, 2008 Share Posted January 13, 2008 14.8 gallons? Is this the number you looking for? miles. Actually the tank takes 15.9, so what is that 14.8? nipper Quote Link to comment Share on other sites More sharing options...
blaze Posted January 13, 2008 Author Share Posted January 13, 2008 miles. Actually the tank takes 15.9, so what is that 14.8? nipper OOPS, You are correct, Forgot about the gallon I put in to get it to the gas station 3 miles down the road. That would be about 15.9 gallon Still not sure what number your exactly looking for? Miles to empty the full tank? (420) Miles after reaching E on gauge? (40) My gas mileage? (26mpg) Can't tell you when the the gas light comes on, still inop. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 13, 2008 Share Posted January 13, 2008 OOPS, You are correct, Forgot about the gallon I put in to get it to the gas station 3 miles down the road. That would be about 15.9 gallon tank. I think the miles was around 420? It was just over 400. thats about right nipper i actually fill up around town at the 280 mark, on the highway 350 mark. i may have to start filling up at the 200 mark just to dull the pain at the pumps. I know same amount of fuel, just easier to swallow in smaller chunks. nipper Quote Link to comment Share on other sites More sharing options...
blaze Posted January 13, 2008 Author Share Posted January 13, 2008 OK, I pulled the dash apart. Checked all the lights, seems to be 3 types, Brown, Black, and Grey. Brown ones illuminate the panel. Black ones illuminate the warning lights(oil-batt-abs-seat belt-CEL, etc). The only one that is different is the Low Fuel Light? Its color is grey (and states this on the circuit card along with 6.5 an arrow pointing to the socket hole), and different in size than any other ones. Seems like there pretty proud of this light, has its own color, unique size, and a name tag on the circuit board. The Low Fuel Bulb is the only one to fail the continuity test. After cleaning the contacts, I applied power and it and it illuminated Its now been reinstalled and waiting to empty a full tank. I'll keep you posted on the outcome. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 13, 2008 Share Posted January 13, 2008 Cougar... you reading this? This fits his thoughts on it's operation. Thanks for the update. Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 13, 2008 Share Posted January 13, 2008 One thing I was curious about is if the light itselt was a 12 volt bulb. Assuming you applied power to it without it being tied to the thermistor, and it didn't blow out, it seems that the bulb is a 12 volt bulb. I think that when the fuel level goes below the thermistor case mounted near the bottom of the tank, the thermistor heats up due to the current running through it and will cause the resistance to go down and turn on the light. It is just a simple series circuit with the bulb and thermistor tied in series between power and grounded through the thermistor case. Quote Link to comment Share on other sites More sharing options...
nipper Posted January 13, 2008 Share Posted January 13, 2008 One thing I was curious about is if the light itselt was a 12 volt bulb. Assuming you applied power to it without it being tied to the thermistor, and it didn't blow out, it seems that the bulb is a 12 volt bulb. I think that when the fuel level goes below the thermistor case, the thermistor heats up due to the current running through it and will cause the resistance to go down and turn on the light. It is just a simple series circuit with the bulb and thermistor tied in series between power and grounded through the thermistor case. Yes, if you watch the bulb, it doesnt turn on. it glows slowly. nipper Quote Link to comment Share on other sites More sharing options...
Skip Posted January 13, 2008 Share Posted January 13, 2008 good work Cat sounds solid kinda got trapped ITH In The House will try and run some 'speriments tomorrow. Quote Link to comment Share on other sites More sharing options...
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