Re: [alfa] Duetto Low Fuel Light

[Caxambu <caxambu@xxxxxxxxxx>]

The fuel tank sender resembles a toilet fill valve. The actual fuel 
"float" (looks like a plastic wine cork) is at the end of a wire rod 
that drives two circuits at its hinge point. That is why there are two 
wires connected to the float assembly sender. One is the fuel level, the 
other is the warning light. I forget which wire is which now.

The fuel level circuit is like a rheostat where the float lever contact 
wipes against a thin coiled wire. The resistance varies according to the 
distance of the contact point along the coiled wire-- this varying 
resistance is what gives the fuel gauge needle its position.

The other circuit is like a simple contact switch, set so that when the 
float rod falls to near the bottom of its travel, the switch contacts 
make contact, closing the circuit to light the warning light.

If you ran dry with the gauge reading 1/3 full and the warning light 
never lit, could be that the float rod is not falling freely along its 
travel, i.e. it could be getting hung up. This would also not allow the 
float rod to drop to the position that would close the contacts for the 
warning light.

First check the wires are making good connection with the sender. The 
sender is grounded via the numerous screws securing it to the tank. The 
tank is grounded via the screws securing it to the body. These are more 
prone to corrosion so carefully check the continuity from the sender 
housing to a good body ground.

To begin troubleshooting the sender:
Set up a spark-free location, open the convertible top (to easily see 
the fuel guage from the rear of the car), clean the area around the tank 
sender, pull the sender from the tank after marking its compass 
position, cover the tank hole with some clean non-sparking material, 
ground the sender to the body (more convenient with wire/alligator 
clips), turn on the electrics, and  move the float rod along its travel, 
observing the fuel gauge needle and warning light. Hopefully you will 
see where it is catching. You may have to tinker with thin nose pliers 
to make adjustments.

--Caxambu
1969 Spider Veloce 1750
Seattle WA




> Date: Sat, 17 Apr 2004 09:28:41 +0930
> From: "The Baylys" <dabaylys@domain.elided>
> Subject: [alfa] Duetto Low Fuel Light
>
> I recently ran out of fuel for the 1st time with gauge reading 1/3 full.
>
> As the light wasn't illuminated I'm asking whether the light operation is a
> function of the tank float or is it independent ?  i.e.: if the float is out
> of adjustment will this affect the light as well ?
>
> My light may well be inoperative, I'm yet to troubleshoot.
>
> Beatle
> '67 Duetto
> Oz
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided