Jump to content

IGNORED

Perplexing "FUEL" light malfunction


dmorales-bello

Recommended Posts

I am afraid I am at a loss for any other help. Let me know if you want to try the rheostat, but I honestly wonder if that will help. The whole system in predicated on a variable resistance. Try used a different light while monitoring the voltage at the lamp connectors. You want to drop that mV reading below what you are seeing now.
I will try the bulbs when I get them at the end of this week and hope at least one of them works. If not I'll hit you up for a rheostat as a final attempt. I'm very thankful for all your help Dave, plus all the insight from @captainobvoius and the others.
I'm still holding on to hope that this "little light problem" won't lick the crowd knowledge base in this amazing forum.

Sent from my SM-N950U using Tapatalk

Link to comment
Share on other sites


in order for that light to come on you have to get much lower resistance, at 12/943 ohms is .013 amps or 130mA seems low. CO needs to chime in...

just guessing really as to the normal operating parameters. maybe it self heat up to a much lower resistance. Must be for the light to come which means the thermistor is sitting in a hot hot pool of gasoline to turn on. maybe 124f is still not that hot, try boiling hot. that has to turn it on with a much lower resistance.

feel free to ignore that last bit about boiling, I am just guessing now, but would like to see that resistance get down to about 100ohms (.1k)

Edited by Dave WM
Link to comment
Share on other sites

in order for that light to come on you have to get much lower resistance, at 12/943 ohms is .013 amps or 130mA seems low. CO needs to chime in...

just guessing really as to the normal operating parameters. maybe it self heat up to a much lower resistance. Must be for the light to come which means the thermistor is sitting in a hot hot pool of gasoline to turn on. maybe 124f is still not that hot, try boiling hot. that has to turn it on with a much lower resistance.

feel free to ignore that last bit about boiling, I am just guessing now, but would like to see that resistance get down to about 100ohms (.1k)

Wouldn't you have to have the thermistor receiving power in order for it to heat up enough to drop the resistance even lower?

 

Sent from my SM-N950U using Tapatalk

 

 

 

Link to comment
Share on other sites

heating from within (current passing thru a resistor)or outside (hot water heating up the resistor) should have the same effect, drop in resistance. I don't know the specs of the thermistor so really just guessing as to what temps things happen. The only hope is a resistor in series with the circuit will keep the already  high resistance (3k) a bit higher to keep the thermal runaway from happening (more heat generated than is dissipated by the fluid surrounding it). adding resistance will how ever limit the overall max current allowed (a fixed resistance in series) so as to limit the brightness the lamp could ever achieve. Sounds like a balancing act that Nissan got right but is hard to reproduce from you experience. Has the vendor commented on any of this? would be nice to hear that they have fielded working units.  

Link to comment
Share on other sites

I've not contacted the vendor waiting for us to come up with a viable solution. I did ask him for a couple of weeks time to try out the second unit he sent but that was before I realized it was having the same issue as the first unit I got from him. He seems very amicable so I don't expect anything negative but... You never know.

Sent from my SM-N950U using Tapatalk

Link to comment
Share on other sites

Well I'm no help on the sensor resistance front. I pulled my HVAC bezel off and measured the resistance. Open circuit. Thinking that maybe I had a bad wire or connector somewhere, I pulled my little access hatch off in the rear and measured it right at the tank. Open circuit.

I know the rest of the system works because if I ground the bulb wire back at the tank, the lamp comes on, but without a working sender, it'll never come on. I don't usually run the tank down so far as to really care, but my warning sender is fubar.

Link to comment
Share on other sites

8 hours ago, Dave WM said:

in order for that light to come on you have to get much lower resistance, at 12/943 ohms is .013 amps or 130mA seems low. CO needs to chime in...

I can help with that tomorrow. I will push current through one of those little bulbs until it starts to "noticeably" glow. The current measured at that point will enable me to extrapolate how low the sender resistance needs to go in order to light the bulb.

I had previously measured the bulb current (directly connected to a power supply) at about 230 mA. So that's "full bright". In order to reach that level, the sender unit would have to drop to 0.0 Ohms. Clearly the current at which the bulb is "noticeable" will be less than that.

Link to comment
Share on other sites

milli often used in electronic terms as 1/1000th

so 1000mA = 1 amp

the math I used was ohm law current in amps=volts / ohms

so you had .943k ohms or 943 ohms (in resistance K is 1000, confusing eh?)

12 volts/943 ohms=

.0127 AMPs

.0127 AMPS * 1000 to convert to milliamps

12.73 mA rounded to 13mA

Lots of times values are stated as milliamps or mA due to the smallish current and its easier to say 130mA that .013Amps

 

Edited by Dave WM
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.