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Fuel tank sender connections.

Posted: Mon Oct 03, 2016 9:12 pm
by simmit
(1). I've studied the wiring diagrams (Mess site) but cannot find the fuel tank sender unit in the drawings, fuel gauge yes but sender no. Possibly my eyes are not up to it so will someone locate the sender in the diagrams for me please.
(2). There are three connections on the/my sender but only two were connected, none of the connectors are marked. Shall be grateful for advice as to whether or not all three ought be connected to the loom and also which connection is which.
(3). The fuel gauge was reading incorrectly, hence why I've taken the sender out (to bend/ fiddle the float height) but it now occurs to me it may have been fitted wrong way up. Which way is correct? From centre line of the sender flange the float moves approx. 2" one way and 4" t'other. Ought it be set with the 2" movement towards bottom of tank or 4"?

Re: Fuel tank sender connections.

Posted: Mon Oct 03, 2016 9:27 pm
by peter freeman
There are five gauges on the top row - the fuel gauge is the middle one and the sender is shown next to it - green wire down to the sender which is a rectangular box with a line through it at about 45deg. One connection will be to earth another to the gauge and the third will be the low level warning lamp

Re: Fuel tank sender connections.

Posted: Mon Oct 03, 2016 9:30 pm
by peter freeman
The float will be the correct way up when the resistance is at minimum with the float high. Float up tank full.

Re: Fuel tank sender connections.

Posted: Mon Oct 03, 2016 10:03 pm
by simmit
peter freeman wrote:There are five gauges on the top row - the fuel gauge is the middle one and the sender is shown next to it - green wire down to the sender which is a rectangular box with a line through it at about 45deg. One connection will be to earth another to the gauge and the third will be the low level warning lamp
Thanks Peter for locating the sender in the diagram (I've now worded(?) my copy). Still confused though as the diagram shows just two connections at the sender not three. I assume green is to gauge but oughtn't there be another coloured cable to the warning light?

Re: Fuel tank sender connections.

Posted: Mon Oct 03, 2016 11:22 pm
by peter freeman
The warning light is not identified on the original wiring drawing and I have not had the need (yet ) to work the wiring out. There is a unidentified lamp on the drawing to the left of the fog lamps which could be the warning lamp - I just don't know. Maybe I will work it out sometime when I don't have other jobs to do on our cars - could be a long while.

Re: Fuel tank sender connections.

Posted: Mon Oct 03, 2016 11:24 pm
by peter freeman
ps - on most ( new ) cars the wire colour is green/orange.

Re: Fuel tank sender connections.

Posted: Fri Oct 21, 2016 4:18 pm
by sturfit
I have just bought a new sender unit and it has 3 terminals whereas the old one only had 2. Graham Walker have told me to use any 2 but none seem to work. Any suggestions?
Thanks
Graham.

Re: Fuel tank sender connections.

Posted: Fri Oct 21, 2016 4:35 pm
by AJL Electronics
Try the body of the sender as terminal 3. Otherwise it could be an isolated type, so one terminal goes to earth and the other to the gauge.

Re: Fuel tank sender connections.

Posted: Fri Oct 21, 2016 4:36 pm
by AJL Electronics
Try the body of the sender as terminal 3. Otherwise it could be an isolated type, so one terminal goes to earth and the other to the gauge. This is a Middlebridge I take it? You need three terminals to retain the low level warning.

Re: Fuel tank sender connections.

Posted: Fri Oct 21, 2016 6:16 pm
by simmit
AJL Electronics wrote:Try the body of the sender as terminal 3. Otherwise it could be an isolated type, so one terminal goes to earth and the other to the gauge. This is a Middlebridge I take it? You need three terminals to retain the low level warning.
The sender (which looks quite new) on MB50 has three terminals but only two are needed yet the warning light still functions and in fact, there are only two connector wires in the loom. Yes, one of the terminals is marked WL (Warning Light?) but it's not needed on MB50. I also found that it doesn't matter which way round I connect the other two the gauge function's fine (but note; if matched to a VDO gauge fix the sender upside down and bend the float position to suit).
Possibly there are several makes of sender with each having different characteristics. If memory serves me well my sender has LAP (maker) mark on it.

Re: Fuel tank sender connections.

Posted: Fri Oct 21, 2016 6:20 pm
by AJL Electronics
The SE6 series need the three terminal type because the lamp is directly wired from the sender. The Middlebridge may use a comparator to indicate low fuel, as the 5a does.