Fuel reserve light / gauge

[hot66]

The light comes on when cornering or braking with the fuel sloshing about .. always has and they all do. All that’s changed now is reserve light used to come on at ‘empty’ when sat still … now comes on just below 1/4 when sat still. Not exactly a major issue but don’t like it when things change for no apparent reason

[Nine One One]

You could always try cleaning the sensor unit itself and testing it?

https://forums.pelicanparts.com/porsche ... tself.html

[hot66]

Frustratingly for me, already had that out , cleaned and checked the output at different levels… it’s fine along with the signal it gives… although admittedly I’ve not measured the volts at the gauge to see if something is happening g between the 2

[Ian Comerford]

Did you get any further with this James?

[hot66]

Not really … if I unplug the power then reconnect it seams to act correct then starts giving false high reading again. Its easy to live with but I would like to understand why it’s happening

[Ian Comerford]

Thank you. Mine seems to be pointing at the gauge being faulty. It reads full when full, goes down to 3/4 and stays around that area until the low warning light comes on. Given how the system works that means the float is reaching the bottom and contacting the low level contact, but it isn’t registering the level most of the way down. It’s manageable but…. Any recommended gauge repairers out there (I know of REAP)?

[hot66]

Similar symptoms to mine Ian

[Ian Comerford]

Hhhmmm. To complicate the diagnosis, this was happening a few years ago so I fitted a new sender. The problem went away for a couple of months and then came back……no idea!

[hot66]

Update Ian … but not really a solution

Started car today, fuel reading 1/4 but reserve light just flickering on …. Popped gauge out whist car was running , removed power and negative , re fitted and the gauge suddenly settled and read as it should, eg needle at empty and light flickering on . Stayed correct for rest of the drive

Not quite sure what this means but it points to the gauge holding charge ?

[Ian Comerford]

Thanks James, got to be worth a try

[hot66]

Thought I’d mended this, but on the weekend same …. Reading at about 1/4 tank on the gauge and reserve light came on … unplugged the power to the gauge and re plugged in and gauge read correctly.

In my head this points to a problem with the gauge ? I’m not sure whether the power to the fuel gauge goes through anything else ? Electrics are my weak spot

[911hillclimber]

FWIW:
I've had this kind of thing with my oil pressure gauge on my 73T, all original.
Only way I fixed it was to run a new fresh wire from one end of the gauge/sensor circuit to the other end. 12 months on and all is well.
I think I have a corrosion or break in the wire, a bell through the circuit showed nothing wrong.

The pressure gauge would show an immediate off the scale pressure reading on start-up and running and then sometimes drop to 'normal' in use.

[Gary71]

Thought I’d mended this, but on the weekend same …. Reading at about 1/4 tank on the gauge and reserve light came on … unplugged the power to the gauge and re plugged in and garage read correctly.

In my head this points to a problem with the gauge ? I’m not sure whether the power to the fuel gauge goes through anything else ? Electrics are my week spot

When you find the fix let me know as mine does the same!

[Ian Comerford]

I’ve had this problem for so long I zero my trip every time I fill up and start looking to refill as it gets to 400 miles or so, knowing there is some to spare. I still find it strange that the reserve light works correctly, but then as with James, electrics are my weak spot

[KS]

Can I just throw another problem into the arena?

The gauge on the 914 never reads full when the tank is brimmed full with fuel - the needle sits between 3/4 and full, but never full. As the fuel level gets low, at just above 'empty' the light comes on as expected. I've checked the sender against the official manual and it all reads fine, but it's just that the gauge is clearly giving a false reading when the tank is full, which then makes a mockery of the intermediate readings. I suspect the gauge is faulty, but maybe just a bad earth, although the bad earth scenario seems to affect the other end of the scale, according to previous posts.