Fuel gauge not working

[Mr B]

Afternoon all,

So the fuel gauge has stopped working, I assumed it would be the connections on the sender unit corroded as per normal, well not this time, checked voltage I have 4.91 volts feeding the sender so I briefly earthed the wire out and the gauge did not move, the water temp gauge is fine but the cluster illumination light that does those 2 gauges is also not working, related?

Any advice would be much appreciated

Wayne

[Andrew 2.8i]

Hi Wayne,
It's the same light that illuminates those two gauges, so the bulb will most likely have blown.
The lighting circuit is not connected to the circuit that feeds the sender, it's just a coincidence if the issues have appeared at the same time.

If you join the two wires on the sender together, the gauge should rise to the top. However, as you're getting the correct voltage, the wiring won't be the issue. I would imagine that either the gauge is faulty or, more likely, the sender itself. If it was me, I would drain the tank to remove the sender to take a look. the float may just be stuck and might need freeing.

Good luck,
Andrew.

[Mr B]

Hi Wayne,
It's the same light that illuminates those two gauges, so the bulb will most likely have blown.
The lighting circuit is not connected to the circuit that feeds the sender, it's just a coincidence if the issues have appeared at the same time.

If you join the two wires on the sender together, the gauge should rise to the top. However, as you're getting the correct voltage, the wiring won't be the issue. I would imagine that either the gauge is faulty or, more likely, the sender itself. If it was me, I would drain the tank to remove the sender to take a look. the float may just be stuck and might need freeing.

Good luck,
Andrew.

Hi Andrew,

Thanks for replying mate, I did touch the two wires together and the gauge didn't move at all so it looks like the gauge itself has malfunctioned, on the brightside I'll have to remove the cluster to get to the blown bulb regardless so 2 birds one stone, incidentally the blown bulb is an LED bulb - it's blown two of them so far and tonight the LED bulb above the speedo has blown as well now, cheap LED lights perhaps? Can you recommend some decent one's please mate

Wayne

[Andrew 2.8i]

incidentally the blown bulb is an LED bulb

Hi Wayne,
I assume that the LEDs have been working at some point, and we can discount the possibility of them having been put in the wrong way?
While the clocks are out it might be worth checking the condition of the printed circuit. Happily, CCI now sell a reproduction replacement if yours is damaged.
When I changed my illumination for LED, I just bought some cheap Chinese ones, just make sure that they emit light all around, don't buy the directional ones. I've now replaced them with green 3W bulbs though.

Andrew.

[pbar]

cheap LED lights perhaps? Can you recommend some decent one's please mate

Just a thought, but might be worth forgetting the LED route and simply replace with normal bulbs, you might wish to remove the bulb covers (if they are still there), and simply use 3W green bulbs. NIce and easy and will be close to original appearance. The originals where 3W also, so be careful if you go higher than that as 30 year old plastics might not take too kindly to the extra heat generated.

[Mr B]

cheap LED lights perhaps? Can you recommend some decent one's please mate

Just a thought, but might be worth forgetting the LED route and simply replace with normal bulbs, you might wish to remove the bulb covers (if they are still there), and simply use 3W green bulbs. NIce and easy and will be close to original appearance. The originals where 3W also, so be careful if you go higher than that as 30 year old plastics might not take too kindly to the extra heat generated.

These ones mate?

[SCP440]

I would be weary of Cheap Chinese bulbs, with the amount of work needed to replace it might be better to pay a bit more and get some with a recognised brand on the box if available.

[pbar]

That's the kind of thing yes, I'd go for 3w, the green bulbs will give an original appearance, but will be brighter without the covers, and the dimmer should also work.

[Mc Tool]

I would be weary of Cheap Chinese bulbs, with the amount of work needed to replace it might be better to pay a bit more and get some with a recognised brand on the box if available.

Ha ha yeah ,the guy selling the name brand bulbs probly gets them in bulk from China and repackages them in posh boxes

[Andrew 2.8i]

You'll probably find there's not a lot of choice when it comes to the coloured dashboard bulbs.
When I was looking for them, it was China or nothing....

Andrew.

[Mr B]

Hi guys,

Hope you all had a good Christmas

Today I went outside and made another attempt at sorting the non working fuel gauge, here is what tried:

Tested power to sender and confirmed 4.98 volts.
Earthed out positive wire to two different earth points - gauge did not move.
Removed instrument cluster and changed fuel gauge - no joy
Replaced entire cluster with a spare I have - no joy
Cluster illumination is fixed so I can now see the gauge isn't working even in the dark lol

No work has been done to the car that could have directly or indirectly effected the gauge.

Any ideas guys cos I'm at a loss with this one

Cheers

Wayne

[Andrew 2.8i]

Any ideas guys cos I'm at a loss with this one

Hi Wayne,
Although this situation can be frustrating, you've eliminated lots of possibilities, so you're definitely making good progress.
It's looking more and more likely that the sender itself is the faulty component.

Andrew

[Mr B]

Any ideas guys cos I'm at a loss with this one

Hi Wayne,
Although this situation can be frustrating, you've eliminated lots of possibilities, so you're definitely making good progress.
It's looking more and more likely that the sender itself is the faulty component.

Andrew

Hi Andrew,

Thanks for replying, taking the sender out of the equation, shouldn't the two wires that go to the sender unit make the gauge go to the top if touched together? If so this doesn't happen when the wires are touched together.

Just reading what I wrote back to myself, in theory it can only be the gauge or the earth wire, and as I have replaced the gauge twice already (can't accept all 3 gauges are bad) it can surely only be a bad earth as I do have a steady 4.98 volts getting to the sender unit.

Wayne

[Andrew 2.8i]

Thanks for replying, taking the sender out of the equation, shouldn't the two wires that go to the sender unit make the gauge go to the top if touched together? If so this doesn't happen when the wires are touched together.

Hi Wayne,
Of course, my bad.

Have you checked that you are definitely getting a live feed at the gauge? Are the contacts on the printed circuit OK?

Andrew.

[pbar]

shouldn't the two wires that go to the sender unit make the gauge go to the top if touched together?

It should yes, and as you have done this test you can leave the sender unit to one side for now. If you are sure that one of the fuel gauges is a working one, then perhaps it might be worth considering the wiring. Are you able to concoct a test/temporary earth wire from the gauge to any unpainted earth point on the car/chassis, and see if the gauge responds at all, either in normal use or with touching the sender wires together again. It's just a thought as this may tell you if it is an earth fault. Good luck with it!

[Caprigear]

Try cutting the two sender wires back at least a foot or so and replacing with new wiring.

[Mr B]

Many thanks guys,

Will try this tomorrow if the weather is dry.

Have a great new year

Wayne

[Mr B]

Happy New Year everyone

Well the fuel gauge is sorted, bit embarrassed by the fix to be honest because after having these cars for over 30 years I think I should have known better- Martin you was spot on, it was indeed the wiring at the back of the car just as you said mate - the earth wire was corroded and broken rendering it useless.

Thanks for all the help guys and a special thanks to Martin -Legend

Kindest regards

Wayne

[pbar]

Excellent, glad you have found the issue Wayne.

[Mr B]

Excellent, glad you have found the issue Wayne.

Thanks mate, one thing I did learn in all this is a way to test the fuel and temperature gauges individually using one of these, I connected the small 9v battery to each post on the back of the gauge briefly and bingo!