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Fuel gauge not reading
We had the 2 Webasto circulation pumps replaced by a very knowledgeable Freightliner service facility here in Minot, ND. I did not notice if it was working when I picked it up but I see my fuel gauge is now not working. Is there something back in the rear of the coach that might be related to the fuel gauge. Loose ground, something in the electronics cabinet above the engine? They are going to take another look on Monday but thought I would throw it out there. I am going to wiggle wires under the dash and around the gauge if I can get access. Any suggestions welcome.
We are heading back to TX next week and would like a working gauge.
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12 Replies
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Fuel sending unit has to come out of fuel tank somewhere, sounds like in the neighborhood of your pumps.wires have to go to gauges.
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Plan “B”
Fuel up, drive / log mileage using probably 5 MPG. Do a little math and you have a backup plan when looking at Prevost fuel gauge.
Knowing better then to trust the fuel gauge for accurate info, I’ve done this on all 3 buses owned. Gave me a better idea of how much fuel I had between fill ups when looking at fuel gauge position.
AL
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I agree with Al. Perhaps it is from flying when endurance was based on hours, with the bus being similar in using miles to determine endurance. I do have one unknown in the bus, and that is how many usable gallons the bus really holds.
My practice has always been to use the total miles driven and total fuel purchased for every year to determine mileage. Prior to the failure of my EGR system every year consistently I was getting 5.9 MPG. When the EGR system stopped working my mileage was a steady 6.5 MPG every year. I have not bothered to try to isolate the fuel used by the Webasto or generator since my use of them seems to follow the same pattern every year and neither of them uses a whole lot of fuel each year.
My listed fuel capacity is 208 gallons. My preference is to avoid truck stops so I created a personal window for refueling between 700 miles and 1000. When I have opted to put 1000 miles on before refueling my fuel gauge shows the needle near or at the bottom. The most I have ever taken on is 174 gallons and when I did refuel the needle indicate the tank was dry and I never got a low fuel warning. If our 208 gallon capacity is a true indication of how many usable gallons I carry I had 34 gallons in reserve. If my true volume of fuel is 90% of that I had about 13 gallons in reserve.
I am not going to run the tank dry to find out. I know from experience the OTR air tends to drop the mileage, as does towing, especially when the toad is a Hummer so I will not tend to push my limits and if my gut suggests a 900 mile limit due to headwinds or mountainous terrain I will stay on the low side of my fuel range for getting fuel.
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So, the thick plottens! The fuel gauge was only getting 12V. The tech made a jumper and got 24V to the gauge working. Where did the 24V go? Country Coach also has a systems monitor which is now reporting low chassis battery voltage (I had these obnoxious voices turned off). So whatever senses 24V is also only seeing 12V. Anyone have any additional thoughts as to what might have been affected to cause a couple of my 24V circuits to revert to 12V?
The Vanner is putting out the correct voltage and the engine is getting the proper voltage. There is this thing in the picture. What does it do?
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The devise you show is a chassis electric system monitor. It will not warn of issues with the house electrical systems.
The monitor instructions are available in detail on the Vanner web site, but the short version is it monitors voltage on the 24 volt side of the electrical system. If the voltage is over 30 VDC, or under 24 VDC it will light up the dash warning light for voltages. It is also monitoring battery balance which is regulated by the equalizer. The battery balance has to be the 12 VDC power has to be 1/2 of the actual 24 VDC power, within about 1/2 volt. The 12 volt power is important because the engine ECM needs 12 V and if it gets down to a low voltage it shuts down the engine.
Whenever I get an electrical system warning light my first response is to pull to a safe spot and verify the input voltages to the monitor are within the required range. If they are OK, but the warning light is on the indication is a failed monitor. In that case I pull the wire at the monitor to extinguish the light. If the monitor is OK the monitor is advising of a needed repair.
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So to simplify and restate the question, what would cause the fuel gauge to lose 24V and suddenly only get 12V. At the same time, the coach monitor that watches the coach 24V announces that it is only seeing 12V?
Jeff and Lindsay
91 Marathon XL -
Bill,
So all of your other gauges have the proper 24 volt reference voltage? Seems weird because i just had my dash apart and i think all of the gauge power supplies were daisy chained from one supply point.
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Just reread your last post and it seems you are saying all of your gauges are only getting 12v. Is that correct?
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All gauges work. The tech said he found the fuel gauge had 12V so he made a jumper from another 24V source and got the gauge working. I agree it’s weird and I won’t really know if it’s correct until I have time to take the dash apart. Somehow the 24V loss is also being reported by the house monitor system which I believe announces the low voltage rather than a dash light illuminating.
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I do know when that Vanner Monitor goes south it will show up as a Battery Balance light on your dash. Replaced it a couple years ago and light went away. Just plug and play.
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Just a dumb question but pumps you had replaced are they 12 volt,if so did they possibly have a wire and connect it to fuel sender by accident.This started after working in that area .
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ck 24 volt feed in and out to ign switch. FWIW going to think this thru. Don’t understand 1/2 voltage supply drop. wire color are red=24V Yellow=12V.. Black=ground on your DC system (stock prevost)
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