silver97ex Posted December 15, 2011 Share Posted December 15, 2011 (edited) So yesterday I was driving home from work and my gas light slowly came on. Approximately 3/4's of a tank in there (I know this for a fact). It went off for about 5 minutes and came back on the rest of the way home. Then this morning it was on all the way to work (22 miles). Gauge still reads correctly, trip odometer working...my Tach doesn't work but it never has This happened about 2 years ago where it came on for about 5 miles and went off, haven't seen it since, till yesterday. I have never seen it come on when I am actually low on gas, only these two times? Any thoughts on what may be going on? Edited December 15, 2011 by silver97ex Link to comment Share on other sites More sharing options...
sewebster Posted December 15, 2011 Share Posted December 15, 2011 Short somewhere to the wire? I think the sensor for the light is different from the regular level gauge, so it could be a problem with the specific sensor as well. Link to comment Share on other sites More sharing options...
silver97ex Posted December 15, 2011 Author Share Posted December 15, 2011 Is there a seperate module somewhere that gets information from the level sensor and the module is what controls the light? I know things are continuously wearing out (233k miles) but I can't stand lights on in the cluster, it is too annoying. Link to comment Share on other sites More sharing options...
adamzan Posted December 15, 2011 Share Posted December 15, 2011 In the FSM there is a wiring diagram, check in the garage section of the board. If you don't feel like fixing it the right way you could always just pull the bulb. Link to comment Share on other sites More sharing options...
Tungsten Posted December 15, 2011 Share Posted December 15, 2011 So yesterday I was driving home from work and my gas light slowly came on. Approximately 3/4's of a tank in there (I know this for a fact). It went off for about 5 minutes and came back on the rest of the way home. Then this morning it was on all the way to work (22 miles). Gauge still reads correctly, trip odometer working...my Tach doesn't work but it never has This happened about 2 years ago where it came on for about 5 miles and went off, haven't seen it since, till yesterday. I have never seen it come on when I am actually low on gas, only these two times? Any thoughts on what may be going on? Let me explain what is actually going on here. Back in the day, when Pathfinders first came out, they had a secondary fuel gauge to monitor the reserve fuel left in the tank. Over time they phased out the secondary gauge with a little fuel light. Some say it was to discourage people from running low on fuel because it's bad for the pump. Now when Nissan replaced the secondary gauge with a light, they did this in a very lazy fashion. They literally just took out the gauge and wired a light into its place instead. When you see the light slowly come on, this is equivalent to the secondary gauge going down. In fact you can still replace that little light with a secondary fuel gauge. As the reserve dries out, the resistor decreases its resistance and increases the voltage to the light until the light glows bright, which means you are out of fuel. Now with that in mind, corrosion on top of the sender can do funky things. Take that fuel sender cover off and take a look at that sender. 1 Link to comment Share on other sites More sharing options...
silver97ex Posted December 16, 2011 Author Share Posted December 16, 2011 I might have to do that Tungsten, thank you. Though last night on my way home from work and everywhere I drove yesterday, the light was off. And it was off this morning as well... Link to comment Share on other sites More sharing options...
1994SEV6 Posted December 17, 2011 Share Posted December 17, 2011 Let me explain what is actually going on here. Back in the day, when Pathfinders first came out, they had a secondary fuel gauge to monitor the reserve fuel left in the tank. Over time they phased out the secondary gauge with a little fuel light. Some say it was to discourage people from running low on fuel because it's bad for the pump. Now when Nissan replaced the secondary gauge with a light, they did this in a very lazy fashion. They literally just took out the gauge and wired a light into its place instead. When you see the light slowly come on, this is equivalent to the secondary gauge going down. In fact you can still replace that little light with a secondary fuel gauge. As the reserve dries out, the resistor decreases its resistance and increases the voltage to the light until the light glows bright, which means you are out of fuel. Now with that in mind, corrosion on top of the sender can do funky things. Take that fuel sender cover off and take a look at that sender. oh @!*%!!?!?!?!?! is this true or did you make that up? That sounds really farfetch'd. TWO fuel guages?!?! pics or it didn't happpen Link to comment Share on other sites More sharing options...
nunya Posted December 17, 2011 Share Posted December 17, 2011 (edited) Again... Research. There pics and proof here on NPORA alone... edit: simple search of "dual fuel gauge" here using that invisible thing in the top right corner and wah laa! http://img852.imageshack.us/img852/6632/imag0087.jpg Edited December 17, 2011 by nunya Link to comment Share on other sites More sharing options...
1994SEV6 Posted December 17, 2011 Share Posted December 17, 2011 Again... Research. There pics and proof here on NPORA alone... edit: simple search of "dual fuel gauge" here using that invisible thing in the top right corner and wah laa! http://img852.imageshack.us/img852/6632/imag0087.jpg WHATTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT mind freak. No, I google'd this for a solid 10 mins. I got every picture of a dash cluster posted on NPORA except this one. Really though, if you google anything for Pathfinders, this site pretty much floods google. Sorry I couldn't find it. That's amazing. I bet they only put the 2nd gauge on WD21s for like a year? So it would be really hard to find Link to comment Share on other sites More sharing options...
JamesRich Posted December 18, 2011 Share Posted December 18, 2011 Let me explain what is actually going on here. Back in the day, when Pathfinders first came out, they had a secondary fuel gauge to monitor the reserve fuel left in the tank. Over time they phased out the secondary gauge with a little fuel light. Some say it was to discourage people from running low on fuel because it's bad for the pump. Now when Nissan replaced the secondary gauge with a light, they did this in a very lazy fashion. They literally just took out the gauge and wired a light into its place instead. When you see the light slowly come on, this is equivalent to the secondary gauge going down. In fact you can still replace that little light with a secondary fuel gauge. As the reserve dries out, the resistor decreases its resistance and increases the voltage to the light until the light glows bright, which means you are out of fuel. Now with that in mind, corrosion on top of the sender can do funky things. Take that fuel sender cover off and take a look at that sender. I hate to prove you wrong because you sound so confident, but YOUR WRONG! The 86.5 and 87 were the only one with a sub fuel gauge that I know of. I have an 88 owner’s manual and it doesn’t show the sub gauge. The sending unit in the tank actually had two rheostats and two floats. One for the main gauge and a small one for the sub gauge. Picture from the 87 FSM (the 87 pics are all scanned by hand) Picture of the wiring for the 87, notice two rheostats on the fuel tank gauge unit. Here a pic from the 94 FSM, it only shows the main rheostat. Picture of the wiring for the 94, only one rheostat. The FSM doesn't have a pic of the sender for the low fuel light but if you ever pulled a sender you will see instead of a rheostat it has a small tube with a floating metallic coated ball. (I'm assuming it's a ball, I never cut one open) When the fuel level drops the ball drops down in the tube and touches a contact turning on the light. See the little tube with the wire going to it? Nissan is not lazy or stupid, they would not put a more expensive sender in a vehicle that does not need it. If your light gets brighter as your fuel level drops it's probably because the metallic ball is dirty and doesn't make good contact when it is lightly touching the ground in the tube. If by chance your tank unit has two rheostats it's because someone replaced it with a unit from an 87 which would be very rare so you need to pull it and send it to me so I can get my sub gauge working. Someone replaced mine before I got the truck with the unit for the light. I have never seen the dual gauge unit. James 1 Link to comment Share on other sites More sharing options...
Tungsten Posted December 18, 2011 Share Posted December 18, 2011 Actually, I have pulled the sender out and I did see the little cylinder mechanism on the bottom. The sender, or any of its components, should never be dirty inside the gas tank because all that stuff is always swimming in gasoline. I think they replaced the bottom float with that little cylinder, which may actually have variable monitoring capabilities. Here is how I can prove this: A regular fillament bulb that sits in that little fuel graphic box will actually take above a certain voltage to turn on. On the other hand, an advanced LED bulb will work with any voltage applied to it. Replace that bulb with an LED and you will see that when you start the truck the LED will light up, which means that there is some voltage there while the truck is running and it will get brighter if you start to get low on fuel. A regular bulb will only start to get brighter after a certain voltage is applied to it but not when there is enough fuel in the tank. I think this calls for some more experimentation! Link to comment Share on other sites More sharing options...
ahardb0dy Posted December 18, 2011 Share Posted December 18, 2011 the sub fuel gauge if I recall would show the fuel from a 1/4 down to empty, the sub fuel gauge broke down the 1/4 of fuel over a broader range on the gauge. I had it in my 87 Hardbody Link to comment Share on other sites More sharing options...
Tungsten Posted December 18, 2011 Share Posted December 18, 2011 That makes sense why it would have two floats then. Once the fuel line got below 1/4 mark it would make the bottom float work like another tank. I wonder if the little cylinder thing works in the same way but just starts much later at like 1/8 of a tank. Anyway, you never want that light to be on in the first place. It is generally a good idea to refuel at the 1/4 mark whenever possible. Doing so will save the fuel pump from burning out because the gasoline actually cools the pump. Link to comment Share on other sites More sharing options...
Reshma Posted December 18, 2011 Share Posted December 18, 2011 Do the 95 SE's have a gas light aswell? Link to comment Share on other sites More sharing options...
Tungsten Posted December 18, 2011 Share Posted December 18, 2011 Yes Link to comment Share on other sites More sharing options...
Reshma Posted December 18, 2011 Share Posted December 18, 2011 Never seen mine turn on. And is there a way I can check to see how big my tank is? The feul gauge is iffy and I'm not sure how big the tank is. Would my iffy fuel gauge affect the light? Sorry to steal the topic. Link to comment Share on other sites More sharing options...
Trogdor636 Posted December 19, 2011 Share Posted December 19, 2011 Never seen mine turn on. And is there a way I can check to see how big my tank is? The feul gauge is iffy and I'm not sure how big the tank is. Would my iffy fuel gauge affect the light? Sorry to steal the topic. Get a little plastic 2-3 gallon gas jug, fill it up, fill up your Pathfinder, and run it till its empty. Use the little plastic can to get you to a gas station, and see how much goes in. Turns out my gas gauge is on E when I have 4-5 gallons left. Link to comment Share on other sites More sharing options...
Towncivilian Posted December 19, 2011 Share Posted December 19, 2011 Actually, I have pulled the sender out and I did see the little cylinder mechanism on the bottom. The sender, or any of its components, should never be dirty inside the gas tank because all that stuff is always swimming in gasoline. I think they replaced the bottom float with that little cylinder, which may actually have variable monitoring capabilities.Here is how I can prove this:A regular fillament bulb that sits in that little fuel graphic box will actually take above a certain voltage to turn on. On the other hand, an advanced LED bulb will work with any voltage applied to it. Replace that bulb with an LED and you will see that when you start the truck the LED will light up, which means that there is some voltage there while the truck is running and it will get brighter if you start to get low on fuel. A regular bulb will only start to get brighter after a certain voltage is applied to it but not when there is enough fuel in the tank.I think this calls for some more experimentation! This description of the LED being faintly lit with the engine on happens with an LED in my Service Engine Soon spot on my R50. I have no idea why voltage is always applied to the SES bulb. Completely irrelevant to this thread, though. Never seen mine turn on. And is there a way I can check to see how big my tank is? The feul gauge is iffy and I'm not sure how big the tank is. Would my iffy fuel gauge affect the light? Sorry to steal the topic. Here is where the fuel light is: I guess a faulty fuel gauge can affect the light if it thinks the tank is empty or something. Link to comment Share on other sites More sharing options...
Tungsten Posted December 19, 2011 Share Posted December 19, 2011 (edited) This description of the LED being faintly lit with the engine on happens with an LED in my Service Engine Soon spot on my R50. I have no idea why voltage is always applied to the SES bulb. Completely irrelevant to this thread, though. Maybe but one of these days I'm going to do some more experimenting. James could be right where they just replaced the float with a switch like device. They did the same thing with the oil pressure gauge too. Pathfinders used to have oil pressure gauges and then Nissan just decided to give you a light instead of a gauge and they replaced the pressure sensing sender with a switch style sender. +1 for that pic I never knew they had this design too. Edited December 19, 2011 by Tungsten Link to comment Share on other sites More sharing options...
Reshma Posted December 19, 2011 Share Posted December 19, 2011 That area between the oil temp and gas that's said PRND21 lights up? Never even seen it on my truck. And never seen that gad light on start up. Time to go get a jug to keep some gas in. Link to comment Share on other sites More sharing options...
Trogdor636 Posted December 19, 2011 Share Posted December 19, 2011 That area between the oil temp and gas that's said PRND21 lights up? Never even seen it on my truck. And never seen that gad light on start up. Time to go get a jug to keep some gas in. Mine never comes on when you turn the ignition on either. I just verified the bulb worked by swapping it with something else that does come on with the ignition key on. I've had horrible luck with low fuel lights on every Nissan I have owned but my 94 2WD Hardbody. Thats the only one that worked on a consistent basis. Like Tungsten said though, its better to fill up before you see it. Link to comment Share on other sites More sharing options...
Tungsten Posted December 20, 2011 Share Posted December 20, 2011 That is correct there is no bulb check for the low fuel light. However, when you turn the ignition on there is a weak voltage across those contacts, which is not enough to turn on the bulb and probably has to do something with the little cylinder mechanism on the sender. When that little thingy on the sender trips from a low fuel level, the light should go on. Link to comment Share on other sites More sharing options...
Reshma Posted December 20, 2011 Share Posted December 20, 2011 Mine never comes on when you turn the ignition on either. I just verified the bulb worked by swapping it with something else that does come on with the ignition key on. I've had horrible luck with low fuel lights on every Nissan I have owned but my 94 2WD Hardbody. Thats the only one that worked on a consistent basis. Like Tungsten said though, its better to fill up before you see it. That is correct there is no bulb check for the low fuel light. However, when you turn the ignition on there is a weak voltage across those contacts, which is not enough to turn on the bulb and probably has to do something with the little cylinder mechanism on the sender. When that little thingy on the sender trips from a low fuel level, the light should go on. Found out My dad has one of those portable tanks that carries a gallon or two. Gunna wait it out till I have like 250 miles on the tank then I will put some gas in the portable and run her till she is empty. Link to comment Share on other sites More sharing options...
1994SEV6 Posted December 20, 2011 Share Posted December 20, 2011 hey everyone..keep in mind, running out of gas is very bad for your fuel pump. To everyone who is like "I'm gonna run it out of gas and keep a 3 gallon jug" dont do that. You are damaging your fuel pump. THAT'S the real reason they took the 2nd gauge out. They put an idiot light in. When people see the light, they KNOW they need gas, but not everyone looks at their gauges all the time. So sometimes they would run out of gas and it would damage the fuel pumps. I guess people got made and complained. People be stupid. Link to comment Share on other sites More sharing options...
Reshma Posted December 20, 2011 Share Posted December 20, 2011 hey everyone..keep in mind, running out of gas is very bad for your fuel pump. To everyone who is like "I'm gonna run it out of gas and keep a 3 gallon jug" dont do that. You are damaging your fuel pump. THAT'S the real reason they took the 2nd gauge out. They put an idiot light in. When people see the light, they KNOW they need gas, but not everyone looks at their gauges all the time. So sometimes they would run out of gas and it would damage the fuel pumps. I guess people got made and complained. People be stupid. Yea I know its bad for the pump but running it out once shouldnt kill it. I hope it doesnt. Its not like I'm planning to do this on a constant basis. One time, just to find out the size of my tank...unless someone else know where else I could find this out? Vin? Or maybe written on the tank somewhere? Link to comment Share on other sites More sharing options...
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