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Low fuel warning light

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Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
Good afternoon,

As you can see by the picture that is the new sender. I have a 1974 1/2 MG MGB. I have upgrade the carb from manual choke to electric, so I now have that spot open on my dashboard. My idea is to install the lamp, but I am not sure how it works. I am thinking it works on ohms when it gets to a certain point sends power to a lamp and it illuminates. I tried hooking up a warning lamp I put one wire on the prong and grounded the other then moved the sender up and down and it does not illuminate. I know I am missing something. I looked online and cannot seem to find a circuit. Any suggestions?

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Attachments:
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RAY 67 TOURER Avatar
RAY 67 TOURER Ray Marloff
Fort Bragg, CA, USA   USA
1967 MG MGB "My Girl"
Most warning lamps work by opening or closing a circuit. Your lamp must be grounded to close the circuit and illuminate it. RAY

Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
Thank you for your response Ray and the info. I probably should have said that the lamp is an ignition warning lamp. Maybe this will not work as well. I was thinking on purchasing the green TD warning lamp. Not sure if that would make a difference. Are you saying that I should wire it all the way to the dash and then try it because I am trying it way to close?

Thanks Chris

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ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
Hi Chris

That ign warning lamp is ideal, it has two isolated contacts. I have sketched how you need to wire it all up, that is assuming that the low fuel warning connector is actually a switch, not just a lower resistance.

Herb



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TonyV Avatar
TonyV Tony V
Rutherford, NJ, USA   USA
1974 MG MGB
I do not know how that sender is supposed to work. If the third terminal is actually intended to be used as a Low fuel warning light, I would expect to see a switch in there. You should be able to determine this using an ohm meter.

Fairfield, CA, USA   USA
why would you need a low fuel warning light? You cannot know how many miles you have driven and what your avg mpg is and rapidly calculate (in your head!) the matter or even look at the gauge (which in my case, a 73 with original stuff, is pretty darn close to dead on) (or with a little time, learn what your gauge means when it is 3/4 empty)

That thing, a "low fuel light"--which means zilch, really, just like "your brakes have failed" light, a fact you damn well better know already is the result of an ignorant federal (or compay) lacky's ignorance. Or, possibly the general using public's ignorance.

Low fuel lights are a display of the electronics that control modern cars and doom them to an early death. Can you imagine someone 20 years from now wanting to restore a 95 BMW? Impossible. no more parts. electronics fried, etc. Or incredibly expensive as to make it silly. An MGB? Easy Peazy ...nothing electronic, nothing someone with a decent senses cannot understand and repair. No Low Fuel light to fuss over.



1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed

ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
Just realised that I didn't attach that sketch.

Herb



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Attachments:
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Low fuel.jpg

Nicecar Avatar
Nicecar Gary (ex "Harv") G
Victoria, BC, Canada   CAN
1980 MG MGB "Red On Red On Red"
When I read the OP, I couldn't understand why go to all this trouble, but didn't want to "rain on Chris's parade".

But after Mac piped in with similar thoughts...

Sometimes many of us can get carried away with little upgrades (that can end up taking massive time and effort once started), simply to express our love for these beasts.

Chris, if living in Colorado, if you haven't already swapped your OE heater valve with a ball valve, that is a worthwhile project.

Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
TonyV

Sorry took so long to reply. You mean check that prong with the ohm meter to see if it reads?



Edited 1 time(s). Last edit at 2017-12-05 04:49 PM by Chris798.

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Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
Hello Herb,

Sorry about the response being so late. Thank you for the response and the diagram sketch provided. I am attaching a picture of how I wired it the first time. I see there is a switch, is that in the sender or is that outside the tank? I hope that you have a great rest of the day.

V.R. Chris


Attachments:
20171205_151835.jpg    14 KB
20171205_151835.jpg

Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
Mac,

You are correct I do not need it, I have a gauge. Although I did update my gauges. I tested my sender and gauge and it does not go all the way full but goes all the way empty. Plus without the manual choke being there, I now have an empty slot, why not add tricks and gadgets? Not to be mean or anything, but would you say the same thing to someone who puts a V-8 in their B? Remember this my MGB and the things that I do to it make it unique to me because I built it how I wanted it. Which is why my gauges are updated, my carb is updated, and my exhaust will be updated. I may convert the rear to modern shocks. Does this take value away from it. I would say if an MGB collector came across my car he would not think of it very highly and would prefer to see it in it's original form and would therefore value it less. Plus think of the conversation when seen when someone asks what that light is for? Then you tell them what it is and they respond, that did not come on that year. I would say you are correct I added it when they updated the sender to include the light so I thought I would make use of it.



Edited 1 time(s). Last edit at 2017-12-05 04:49 PM by Chris798.

Chris798 Avatar
Chris798 Chris S
Littleton, Colorado, USA   USA
1974 MG MGB "B-26354"
Gary,

It is also not just about doing it to the MGB. It is about getting the knowledge to put something together, how to do it right and make it work possibly for something else or you can use the same concept for another switch. I do not know, be creative. Thank you for the advice on the water heater, I am aware of it and was thinking of replacing them when the water tank goes.



Edited 1 time(s). Last edit at 2017-12-05 04:48 PM by Chris798.

RAY 67 TOURER Avatar
RAY 67 TOURER Ray Marloff
Fort Bragg, CA, USA   USA
1967 MG MGB "My Girl"
Mac, my '84 Honda Shadow 700C has a low fuel warning light and it's still functioning after 3 decades of work. RAY

Team DNF Avatar
Team DNF David Dobbins
Kansas City, Missouri, USA   USA
In reply to # 3640291 by Chris798 Mac,

You are correct I do not need it, I have a gauge. Although I did update my gauges. I tested my sender and gauge and it does not go all the way full but goes all the way empty. Plus without the manual choke being there, I now have an empty slot, why not add tricks and gadgets? Not to be mean or anything, but would you say the same thing to someone who puts a V-8 in their B? Remember this my MGB and the things that I do to it make it unique to me because I built it how I wanted it. Which is why my gauges are updated, my carb is updated, and my exhaust will be updated. I may convert the rear to modern shocks. Does this take value away from it. I would say if an MGB collector came across my car he would not think of it very highly and would prefer to see it in it's original form and would therefore value it less. Plus think of the conversation when seen when someone asks what that light is for? Then you tell them what it is and they respond, that did not come on that year. I would say you are correct I added it when they updated the sender to include the light so I thought I would make use of it.

Chris

Funny how certain projects are acceptable while others are deemed a waste of time. Make it yours and let the detractors pound sand.

Dave

lgorg Avatar
lgorg Larry Gorg
Renton, WA, USA   USA
1966 MG MGB "Robbie"
I believe that you need to find another use for your former choke hole. I research through Astley's book, MGB Electrical Systems, for fuel sender. A fuel sender has two connections, one goes to the guage, and the other is the ground. I then went to Moss Motors UK web site, which brought me back to the Moss Motors USA site's Supplemental Information for 3 60 - 661 _AHU1027 SENDING UNIT,FUEL, SOLID STATE. It says to ignore the terminal with the blue prong. Actually, I wanted to see what other applications this unit had, so did a search on the AHU1207 part number. All I could find was that this fits MGB and MGC. The MG Owners Club (MGOC) has a wiring diagram that shows how it is suppose to work.

What appears to be missing, is a switch to enable a light to come on when the rheostat crosses a certain point. That switch would need power going into the sender unit, as well as a wire coming out to feed a light. If you know how the gauge works, it takes power from the gauge that goes to the sending unit's rheostat. The resistance of the rheostat connected to the ground allows the gauge to work. In short, you can't run two things off the power to the sending unit, without altering how the gauge works, thus you would need two more wires in the harness. Perhaps an electrical engineer might know of a different way, but my mind is simple, so I gave you a simple answer.

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