Low Fuel Light...Possible? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

roll_the_dice · 08-25-2021, 04:55 PM

So I don't really trust my fuel gauge. I ran out once already when the gauge said I had 3/8 of a tank. As I was filling up this morning, I thought of a low fuel light when the tank only had 3 gallons left or so. I was thinking of using the tandem lock indicator on the dash for this light and changing the wording to "fuel reserve" or something. I have used low level sensors and such in fish tanks to signal water topoff, but obviously water isn't combustible...not sure about the sensor triggering a 12v source for the light. Any thoughts??

**The Rocknrod** · 08-26-2021, 07:14 AM

Could you use a switch like this? https://www.amazon.com/Current-Sensi...a-660687002639

roll_the_dice · 08-27-2021, 11:34 AM

I honestly don't know...Is a low fuel light triggered by ohms like a fuel gauge or a separate float that triggers the light.

**The Rocknrod** · 08-27-2021, 12:51 PM

I was thinking the switch would trigger a light?

gmtech68 · 08-28-2021, 01:33 AM

Iirc, low fuel lights still read from the stock sender with a logic circuit to turn on the light.

**nsb29** · 08-28-2021, 10:05 AM

I have a low fuel sending unit it’s called a left turn comes on around a quarter of a tank 🤣

ACK · 08-28-2021, 07:40 PM

Have ya' considered putting a slight bend in the sending unit arm to adjust where the fuel gauge is pointing to? Just need to know roughly how many miles you get on a full tank and then adjust when it's close to empty. I'm sure a very, very small bend would make a big difference, then repeat to fine tune things if you have to. If you choose this route, tracing the arm onto a piece of cardboard for future reference would help take some of the guess work out of adjusting if it's not quite right the first time.

roll_the_dice · 08-30-2021, 09:59 AM

I am about to finish up some new wood bed...when I install it, I am going to try and come up with something or just keep filling up when the gauge reads just below half. I am not getting the best MPG either...and it isn't consistent. I have gotten 19.9 once (awesome) and below 10 once (UGH)...but usually hovers in the 11.5-14 range...usually towards the lower numbers. I just thought with a new crate engine and an EFI system, I should get around 15 minimum. Most of my drives are on a divided highway at 55-60 MPH at 8-10 miles...then a little city driving. Maybe I just need a better tune, but that is an entirely different thread....

Mostly was am brainstorming ideas to have a new light in the truck that is useful.

roll_the_dice · 08-30-2021, 10:25 AM

OK, so I finally found a thread on a truck forum that shall not be named...and they have this same basic thread...and someone used this voltage comparator tapped into their sending unit wiring.

Basically it has 12v power & ground to the comparator and a light 12v and ground, then adjust the brass knob until the desired voltage level to turn the light on. For $5 I may try it.

**The Rocknrod** · 08-30-2021, 10:37 AM

Cool, for $5 you can't loose.

Short 3/4 · 08-30-2021, 02:12 PM

Quote:

Originally Posted by roll_the_dice

OK, so I finally found a thread on a truck forum that shall not be named...and they have this same basic thread...and someone used this voltage comparator tapped into their sending unit wiring.

Basically it has 12v power & ground to the comparator and a light 12v and ground, then adjust the brass knob until the desired voltage level to turn the light on. For $5 I may try it.

Looks too good to be true. Please keep us all posted

verdell · 08-31-2021, 09:48 AM

Quote:

Originally Posted by ACK

Have ya' considered putting a slight bend in the sending unit arm to adjust where the fuel gauge is pointing to? Just need to know roughly how many miles you get on a full tank and then adjust when it's close to empty. I'm sure a very, very small bend would make a big difference, then repeat to fine tune things if you have to. If you choose this route, tracing the arm onto a piece of cardboard for future reference would help take some of the guess work out of adjusting if it's not quite right the first time.

This is basically what I did too. Just slightly bent the arm to get it close and actuated it with the switch in the "on" position to mimic the fuel level until I was comfortable with it.

roll_the_dice · 08-31-2021, 09:58 AM

Also saw this metermatch It can trigger light for a low or high setting and adjust the fuel gauge readings...can also be used for temp, oil gauges, etc. but pricey.

roll_the_dice · 08-31-2021, 01:57 PM

OK, so I just ordered a MeterMatch direct from the MFG for $65 shipped...hopefully it will solve my issues and give me the low level light I want. Will update after I install it.

68 P.O.S. · 03-08-2022, 03:50 PM

Any updates on this? I'm thinking of doing this as well

roll_the_dice · 03-10-2022, 10:13 AM

Quote:

Originally Posted by 68 P.O.S.

Any updates on this? I'm thinking of doing this as well

Unfortunately not. I did buy the metermatch, but got caught up in life and now moving across country. I will get around to it, but I am not the fastest sometimes.

**pdxhall** · 03-10-2022, 11:25 AM

Where are you moving to?

Gotenntitans · 03-10-2022, 01:00 PM

Quote:

Originally Posted by nsb29

I have a low fuel sending unit it’s called a left turn comes on around a quarter of a tank 🤣

Yeah, it's sound activated........the SLOSH.

roll_the_dice · 03-10-2022, 01:32 PM

Quote:

Originally Posted by pdxhall

Where are you moving to?

Well maybe not moving across the country, but moving up the east coast 1000 miles...to the Syracuse, NY area.

theastronaut · 03-11-2022, 02:49 PM

You'll need to cut open the tank and add baffles to keep the fuel from sloshing, or else the light will be flashing on and off constantly.

68 P.O.S. · 03-15-2022, 02:33 PM

Ah, good call

**Thealien** · 03-15-2022, 04:45 PM

Quote:

Originally Posted by theastronaut

You'll need to cut open the tank and add baffles to keep the fuel from sloshing, or else the light will be flashing on and off constantly.

I don’t think it would be a problem until probably a quarter of a tank? That’s usually about where I fill up anyway. It will be interesting to see how it works.

68 P.O.S. · 04-28-2022, 03:08 PM

I wonder if it would be possible to use one of these? https://www.camarocentral.com/1968_1..._p/con-29a.htm

**The Rocknrod** · 05-08-2022, 04:17 PM

The simplest hookup would be +12v and ground to the left blue block (#1 and 2). Then tap into the two wires going to your sender and connect to the white connector (#10 and 11).
Attach the full gauge voltage to 10 and the sender return to 11.
If you are almost empty, the wire on 11 will be much lower voltage. Adjust the screw (9) to internally reduce the reference voltage on #10 until the relay trips, sending +12v power to the light from relay #5. Done. If the tank has more fuel (and more sender voltage), the light is off.
https://www.ebay.com/itm/40120428441...IAAOSwPzhZ8p1A

64shortbox · 05-09-2022, 12:17 PM

Master Chief,
Thanks for posting that info. Besides my 64 C-10 I also own a 62 Pontiac. Many years ago I bought a Speedometer cluster with the Speed Alert & Low Fuel light option for my Catalina. It didn't come with electronics to make the Low Fuel light come on. Once I get my truck finished then it's on to my Pontiac to get it done.

08-26-2021, 07:14 AM	#2
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Low Fuel Light...Possible? Could you use a switch like this? https://www.amazon.com/Current-Sensi...a-660687002639 __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

08-27-2021, 11:34 AM	#3
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Re: Low Fuel Light...Possible? I honestly don't know...Is a low fuel light triggered by ohms like a fuel gauge or a separate float that triggers the light. __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

08-27-2021, 12:51 PM	#4
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Low Fuel Light...Possible? I was thinking the switch would trigger a light? __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

08-28-2021, 10:05 AM	#6
nsb29 Senior Member Join Date: Feb 2014 Location: new smyrna beach fl / 29 palms cal Posts: 1,727	Re: Low Fuel Light...Possible? I have a low fuel sending unit it’s called a left turn comes on around a quarter of a tank 🤣 __________________ Hand made A/C vent manifolds for 64-66 trucks adapts any aftermarket A/C to OEM vent

08-28-2021, 07:40 PM	#7
ACK Registered User Join Date: Oct 2012 Location: Philly, PA Posts: 540	Re: Low Fuel Light...Possible? Have ya' considered putting a slight bend in the sending unit arm to adjust where the fuel gauge is pointing to? Just need to know roughly how many miles you get on a full tank and then adjust when it's close to empty. I'm sure a very, very small bend would make a big difference, then repeat to fine tune things if you have to. If you choose this route, tracing the arm onto a piece of cardboard for future reference would help take some of the guess work out of adjusting if it's not quite right the first time. __________________ My truck ain't dead, it just smells funny.

08-25-2021, 04:55 PM	#1
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Low Fuel Light...Possible? So I don't really trust my fuel gauge. I ran out once already when the gauge said I had 3/8 of a tank. As I was filling up this morning, I thought of a low fuel light when the tank only had 3 gallons left or so. I was thinking of using the tandem lock indicator on the dash for this light and changing the wording to "fuel reserve" or something. I have used low level sensors and such in fish tanks to signal water topoff, but obviously water isn't combustible...not sure about the sensor triggering a 12v source for the light. Any thoughts?? __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

08-28-2021, 01:33 AM	#5
gmtech68 Registered User Join Date: Aug 2008 Location: Devon, Alberta Posts: 24	Re: Low Fuel Light...Possible? Iirc, low fuel lights still read from the stock sender with a logic circuit to turn on the light.

08-30-2021, 09:59 AM	#8
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Re: Low Fuel Light...Possible? I am about to finish up some new wood bed...when I install it, I am going to try and come up with something or just keep filling up when the gauge reads just below half. I am not getting the best MPG either...and it isn't consistent. I have gotten 19.9 once (awesome) and below 10 once (UGH)...but usually hovers in the 11.5-14 range...usually towards the lower numbers. I just thought with a new crate engine and an EFI system, I should get around 15 minimum. Most of my drives are on a divided highway at 55-60 MPH at 8-10 miles...then a little city driving. Maybe I just need a better tune, but that is an entirely different thread.... Mostly was am brainstorming ideas to have a new light in the truck that is useful. __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

08-30-2021, 10:25 AM	#9
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Re: Low Fuel Light...Possible? OK, so I finally found a thread on a truck forum that shall not be named...and they have this same basic thread...and someone used this voltage comparator tapped into their sending unit wiring. Basically it has 12v power & ground to the comparator and a light 12v and ground, then adjust the brass knob until the desired voltage level to turn the light on. For $5 I may try it. Attached Images __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

08-30-2021, 10:37 AM	#10
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Low Fuel Light...Possible? Cool, for $5 you can't loose. __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

08-31-2021, 09:58 AM	#13
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Re: Low Fuel Light...Possible? Also saw this metermatch It can trigger light for a low or high setting and adjust the fuel gauge readings...can also be used for temp, oil gauges, etc. but pricey. __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

08-31-2021, 01:57 PM	#14
roll_the_dice Registered User Join Date: Mar 2016 Location: Manlius, NY Posts: 1,698	Re: Low Fuel Light...Possible? OK, so I just ordered a MeterMatch direct from the MFG for $65 shipped...hopefully it will solve my issues and give me the low level light I want. Will update after I install it. __________________ 1965 C10 LWB Stepside 1964 GMC 1 Ton Dually Instagram #notaratrodnotashowtruck

03-08-2022, 03:50 PM	#15
68 P.O.S. Registered User Join Date: Jan 2007 Location: Puyallup, WA Posts: 1,662	Re: Low Fuel Light...Possible? Any updates on this? I'm thinking of doing this as well __________________ 72 C10 lwb fleetside -stock 350/350 combo

03-10-2022, 11:25 AM	#17
pdxhall Senior Member Join Date: Mar 2011 Location: Tucson, Arizona Posts: 2,087	Re: Low Fuel Light...Possible? Where are you moving to? __________________ Sanity'66 http://67-72chevytrucks.com/vboard/s...d.php?t=515110 Long bed, Fleetside, Small back window I've Done So Much, With So Little, For So Long, That Now I Can Do Anything With Nothing.

03-11-2022, 02:49 PM	#20
theastronaut Registered User Join Date: May 2011 Location: Anderson SC Posts: 3,908	Re: Low Fuel Light...Possible? You'll need to cut open the tank and add baffles to keep the fuel from sloshing, or else the light will be flashing on and off constantly. __________________ Project Goldilocks '66 C10 Short Fleet BBW Build '65 C10 Highly Detailed Stock Restoration Thread '78 Camaro Targa Roof Build '55 International Metal/Body/Paint Work '66 F100 Full Rotisserie Restoration '40 Packard 120 Convertible Coupe Restoration How To Restore and Detail an Original Gauge Cluster How To Detail Sand Body Panels, Edges, Corners, Etc



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03-15-2022, 02:33 PM	#21
68 P.O.S. Registered User Join Date: Jan 2007 Location: Puyallup, WA Posts: 1,662	Re: Low Fuel Light...Possible? Ah, good call __________________ 72 C10 lwb fleetside -stock 350/350 combo

04-28-2022, 03:08 PM	#23
68 P.O.S. Registered User Join Date: Jan 2007 Location: Puyallup, WA Posts: 1,662	Re: Low Fuel Light...Possible? I wonder if it would be possible to use one of these? https://www.camarocentral.com/1968_1..._p/con-29a.htm __________________ 72 C10 lwb fleetside -stock 350/350 combo

05-08-2022, 04:17 PM	#24
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Low Fuel Light...Possible? The simplest hookup would be +12v and ground to the left blue block (#1 and 2). Then tap into the two wires going to your sender and connect to the white connector (#10 and 11). Attach the full gauge voltage to 10 and the sender return to 11. If you are almost empty, the wire on 11 will be much lower voltage. Adjust the screw (9) to internally reduce the reference voltage on #10 until the relay trips, sending +12v power to the light from relay #5. Done. If the tank has more fuel (and more sender voltage), the light is off. https://www.ebay.com/itm/40120428441...IAAOSwPzhZ8p1A Attached Images __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

05-09-2022, 12:17 PM	#25
64shortbox Registered User Join Date: Jan 2011 Location: Tulare, CA Posts: 735	Re: Low Fuel Light...Possible? Master Chief, Thanks for posting that info. Besides my 64 C-10 I also own a 62 Pontiac. Many years ago I bought a Speedometer cluster with the Speed Alert & Low Fuel light option for my Catalina. It didn't come with electronics to make the Low Fuel light come on. Once I get my truck finished then it's on to my Pontiac to get it done.

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