Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hi all,

Does anyone know wheres the easiest to find a signal for the fuel sender level unit?

I think from memory its a BLUE/BLACK wire?!

Thanks.

It is indeed a blue wire with black tracer.

The wire goes from fuel level sender unit "P4" located on the front of the tank close to the rear of the rear footwell / front of the bench seat.
You can see the loom enter the car near the end of the pipe on the car floor.



The wire travels to the big connector in the UK passenger side footwell "X6".
Pin number 34.





From here the wire goes to two places.

Pin 7 of the instrument cluster- connector X21 pin 7.
This connects to the gauge itself 'P1'.



The wire from X6 also goes to the yellow board computer connector pin 26 (for analogue speedometer).

The yellow plug in the centre of the dash panel.





I believe it is board computer pin 8 if you have the digital speedometer cluster.

For info - I have the Astra GTE MK2 cluster, and I still use board computer pin 26.

For info....

ALL gauges are fed 10 volts via the To220 three-legged transistor thingy on the back of the instrument cluster.
This is a voltage regulator to ensure that a continuous 10 volts is used, no matter what voltage the battery and alternator are kicking out.
Anywhere between 12.5 and 14.9 volts.

Apologies for those seasoned Cavalier junkies that know this already.

But worth mentioning anyway.

The same style of voltage regulator set-up is used on the gauges of all the makes and models that I have worked on. VW, Austin Rover, Vauxhall etc...

So for ease of connection I would say any of..
Floor connector X6 pin 34
Or
instrument cluster X21 pin 7.

I presume the board computer uses an internal voltage comparator to achieve it's readings as it gets an ignition live feed, not 10 volts.

If you are connecting your own gauge, ensure that you follow the manufacturers instructions for voltage supply side of things.
Connecting to ignition live directly may otherwise cause over-reading, and for the gauge value to move up and down with engine revs and electrical load drawing from the battery.

Excellent info as usual Robsey, cheers!
I wonder what triggers the yellow low level fuel light and then the red light?

There should only be one yellow light. Not red.

I assume it it something within the gauge wiring, so that it triggers a warning light beyond a certain resistance value between the sender and the gauge.

Again, many vehicles of this era use the same arrangement.