Fuel gauge says full

[unicorn]

Hi all my fuel gauge says full all the time ( low fuel light works ) . I have replaced the gauge with a tested one from Robsport so ruled that out an just replaced the sender with a brand new one also from Robsport I'm now £60 down and gauge still reads full. I'm assuming the wiring is now at fault so which of the wires is likely to be at fault, where are the trouble spots ( looks ok where it goes through rear of tunnel ) and if all else fails could I bypass a wire from the sender to gauge ( even if only to test the circuit )
Thanks in advance
Chris

If it makes you smile it's the right car

[jclay (RIP 2018)]

You have a short in the Green/Black wire from the sender. It is probably at the point where the wiring harness goes though the clip at the back of the drive shaft tunnel and into the body. You will have to remove the console storage box to pull up the carpet and get to the harness. The Green/Black wire is a straight shot to the gauge. The Green/Orange wire goes to the delay unit and then to the warning light.

Clay

[url="http://www.jclay.me/"]My Triumph Site[/url], [url="http://www.triumphtechnical.me"]Technical Stuff[/url], [url="https://docs.google.com/folder/d/0B8MWEvqOpX3udEF4SmFQUW9RS09hbU5uNW5Wd0xrUQ/edit"]My Public Folder[/url],

[unicorn]

Hi jclay thanks for the reply I have just eliminated black green wire traced from sender to dash and couldn't find any short so connected a wire directly from the sender to the wire on the multiplug cutting out the original as a test but still reads full. I have also tried 4 gauges 2 read full 2read empty also replaced whole instrument pod to eliminate the flexy plastic circuit Do you have any other ideas please
Thanks
Chris

If it makes you smile it's the right car

[jclay (RIP 2018)]

Well, that only leaves one thing, well maybe two.

First though is that the printed circuit board on the back of the bod is bad. (but you checked that!) or

Second, you have the ground wire and the sending wire reversed on the sender unit.

When you turn off the key, does the gauge go to empty? If so, then it means that the gauge is getting power. The sender unit is really a potentiometer that goes to ground completing the circuit. The power for the whole system comes from the gauge. When the car is running and the gauge reads empty, then there is no power running through the gauge. If it reads full, the the circuit is complete and there is full power going through the gauge.

Clay

[url="http://www.jclay.me/"]My Triumph Site[/url], [url="http://www.triumphtechnical.me"]Technical Stuff[/url], [url="https://docs.google.com/folder/d/0B8MWEvqOpX3udEF4SmFQUW9RS09hbU5uNW5Wd0xrUQ/edit"]My Public Folder[/url],

[unicorn]

Hi jclay with the key off the gauge reads empty. The wires are correct with ground on the ground and black green on the correct terminal ( bottom )

If it makes you smile it's the right car

[sonscar]

It is just possible that all the gauges are faulty,with different faults,you could just be that unlucky.I repaired my fuel gauge when it went faulty reading full all the time.I was lucky to find the fault and the repair was tricky but has so far held.These instruments are very fragile looking and age is not on their side.Steve...

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mine
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[unicorn]

Hi sons car that's the way I'm thinking as I have exhausted everything else I can think of I'm going to rig up a test on the bench with my old sender unit that I've tested and it works and gives the variable resistance I need to check them out


If it makes you smile it's the right car

[unicorn]

Hi and thanks to everyone for the help finally got it working I went back to my original idea that the gauge was faulty and worked out how to wire it up on the bench. Turns out my original was faulty so were 2 spares I had and so were 2 others I bought. I finally got hold of one that works. If anyone is interested I will write a guide showing how to test on the bench
Thanks again
Chris

If it makes you smile it's the right car

[nervousnewowner]

well worked through, also just noticed your local, ish have to have a meet up sometime. [:D]

project dhc sold sadly, but project fhc taking over... Dave...

1977 TR7 FHC ongoing restoration
1998 Celica 1.8 ST up for sale
mk 3 mondeo 1.8 daily driver with clutch slipping like mad and half the front bumper left on blaenavon mountain and a 4.30am black ice spin

the new project at birth, watch it evolve...I hope...

[unicorn]

Hi Dave always nice to meet up with fellow wedgies we are a friendly bunch lol I am a member of Glamorgan classic car club and go to a few shows around here I believe there's 1 on in Cardiff on May 17th I enjoy the shows but I prefer to just get out and drive one of my tr7s just for the love of it
Keep in touch or find me on Facebook Chris jones from Rhondda can't miss the pic of my 7 on my profile

If it makes you smile it's the right car

[nervousnewowner]

yeah tempting to head for that myself, like tenby for hols myself, if your ever heading cwmbran way let us know. [:D]

project dhc sold sadly, but project fhc taking over... Dave...

1977 TR7 FHC ongoing restoration
1998 Celica 1.8 ST up for sale
mk 3 mondeo 1.8 daily driver with clutch slipping like mad and half the front bumper left on blaenavon mountain and a 4.30am black ice spin

the new project at birth, watch it evolve...I hope...

[g4zur]

HI I did write a test procedure for the fuel gauge with all readings. Sometime last year. Should be able to find it on here.
Regards Gareth.

G.P.Albrighton