Red Low Level Fuel Light

[GMAN]

Hi,
The red low level fuel light is on permanently but the fuel indicator seems to work OK. Can anyone suggest the possible cause and remody.

Thanks
Graham

[rwmastel]

May I recommend you create a signature so your cars' model year is on each post you make?  Earlier 230SLs had a different in-tank fuel sender unit and maybe that makes a difference here?

[BobH]

Hello Graham, the lamp is fed from contacts in the fuel sender, so it could be a bad sender, if you pull the plug from the sender in the boot, see if the light goes out.  If not report back and we can suggest other tests to try

[GMAN]

Hi Bob,
Unplugged it. Red light went out. I cleaned of the pins and re-tried the plug but the light comes on. The fuel guage reads more than 1/2 so its not that.

[GMAN]

The car is a 1966 230sl auto.

[BobH]

Sounds like the contact in the bottom of the sender is either shorting out due to a build up of crud, or the wires are shorting out.  The internal contact should be open circuit until the float drops when the fuel level is almost empty.  It's a different circuit to the gauge, so that's why the gauge is still working.  They can be taken apart carefully, might be worth a look inside.  I assume it's the cylindrical type rather than the one with the external float.  Best disconnect the battery before pulling it out

https://www.sl113.org/wiki/Fuel/SenderUnit

[Pawel66]

If it goes off when you unplug and back on when you put the plug back on - I am pretty sure it is the switch in the sender. It disconnects the ground. If there is ground on the pin that goes to the plug, the light will be on.

Removing the sender is not that difficult. You need to be careful as you work with fuel, undo the nuts carefully not to break off the studs and have a new gasket at hand.

[GMAN]

Thank you gentlemen.
Ive ordered the gasket and started blasting the nuts with release agent - they are a little crusty. I'll update you later this week once the gasket turns up.

[rwmastel]

GMAN,

Nice signature line.     Also, welcome to the Group!  I see you recently joined.  We have a lot of active members in the UK, I'm sure you'll have opportunities to meet up in person and get to know people.

[GMAN]

Too much corrossion on the old sender to had to replace it.
All good now

[Pawel66]

You replaced the sender and it all works?

[GMAN]

Yeh,
100% all good. Next the Kick-down switch !!!

[Pawel66]

Lovely, thank you. I was worried you got into trouble with sender/gauge compatibility.