Fuel Sender Wiring

[mikea4tdi]

I really need to get my fuel gauge working again, it feels like I'm playing russian rulet everytime I go out!

I put a second hand sender in when I rebuilt the car (thanks Norman!) I assume this is working.

Its the older style sender with just one connector coming out the middle with a standard spade terminal on the end.

The wiring from the car had a spade terminal but there was another wire (green from recollection) that looked like it had the connector cut off.

Just connecting the one wire to the sender is not working. So in summary should both wires be connected to something. There is a chassis earth bolt near the fuel tank with a wire on it, i'm sure that the fuel tank is earthe is that matters.

Any thoughts?

M

Edited by mikea4tdi on Tuesday 22 September 11:49

[Gerald-TVR]

Mike ask Barkychoc tubbystu he posted diagrams of the different types of senders some time ago

Edited by Gerald-TVR on Tuesday 22 September 13:21

[mikea4tdi]

I remember that post but dont' think mine was covered.
Will look again

[kenpage]

mike the other wire you have is the earth, on my orig tank there was a terminal soldered to it for the wire but on the new tank there was no terminal, just put the wire to an earth on the chassis and all should be ok

[tvrgit]

kenpage said:

mike the other wire you have is the earth, on my orig tank there was a terminal soldered to it for the wire but on the new tank there was no terminal, just put the wire to an earth on the chassis and all should be ok

Agreed, you can earth it to anything, not necessarily just the tank.

[mikea4tdi]

Great thats what I was hoping, just wondered why it had the connector cut off by the last owner!
Will get it earthed to the chassis tonight. From recollection one wire is black one is green or green and black, I'll check the wiring diagram to see which one goes to the sender and which is earth.

m

[jimed]

On my S3C the earth for the rear lights, etc. is on the chassis at the front top n/s of the fuel tank so its quite handy for that.
Jim

[GreenV8S]

Rather than assume it's working, I suggest you measure the resistance at different fuel levels and make sure it does change, in the right direction, between the terminals that you expect. You can easily check the gauge by putting a known resistance between the terminals normally connected to the sensor, and see what resistance values are needed to show empty, half full, full.

[tubbystu]

Here you go - the official factory drawing no less Gawd bless 'em.





The bottom one is the one that is/was available from TVR Carparts IIRC

Edited by tubbystu on Tuesday 22 September 22:11

[Le TVR]

If this is the old sender type then the Red-White goes to the centre terminal and the Green to a spade terminal attached under one of the mounting bolts.
Dont earth it anywhere else if you want reliable operation! The gasket insulates and the bolts are no guarantee of a clean connection.

Sender should be 0 ohms (full) down to 350 ohms (empty). ISTR that half full was around a 100.

[mikea4tdi]

Thanks for the tips,
As I have two wires and only one is connected this will be my first fix.
If this doens't work then I'll start checking resistances.
It is the top one in the picture

M

[Gerald-TVR]

Hi Mike

does this help?

As you can see the earth wire, black is conneted directly to the tank, I think if you connect it to a chassis earth you will have problems as the tank should be insulated by rubber from the cradle and the fixing straps. The wire to the sender unit is green/black (ignore the added bit that was done by me

[mikea4tdi]

That helps.
don't think I have an earth point like that on the tank., Will have a play to see what works best, either earth to tank or earth to chassis.
Thanks

Mike