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Jun 15, 2014 3:26 pm
Jun 15, 2014 3:26 pm
Subject: fuel gauge
Who knows how the fuel gauge on the 2ltr works? probably it is the same on many other cars?
My fuel gauge was reading very low (about half or less of what it should). It thas 3 connectors. One is ground, one connected to the fuel tank sender and one is +12V (my car is on negative earth). I removed the gauge, because the fuel tank sender resistance seemed reasonable.
I removed the gauge from my MGA to compare. The one from the MG is like described well on the internet (http://mgaguru.com/mgtech/electric/fg_01.htm): it has 2 coils: one called the "full" coil, one called the "empty" coil, both are connected on one point which is connected to the resistor on the fuel tank. The other ends are connected to ground and 12V. Measuring the resistance between the 3 connections gave 100 Ohm, 100 Ohm and 200 Ohm which makes sense (1 coil, the other coil and both together).
The gauge from the Lagonda is different: it has 180 Ohm between all 3 points. (how does this work with 2 coils, may be the upper one has a connection in the middle too). When I connect the gauge to ground and +12V, I could get it showing half full. Connecting the third to either ground or 12V would let it show empty or full. But that is not what the fuel tank sender delivers. The fuel tank sender connects more or less to ground only. On my gauge this leads to a value between empty and less than half full.
I opened the gauge (glas removed, face removed), see picture. I do not understand how it works, nothing seems broken, no possibility to adjust and however I connect it it does not do what it should. Was it made for a different type of fuel tank sender?
The only solution I see so far would be to buy a "normal" one (e.g. MGA) and put the face of the Lagonda instrument in.
Attachments:
Who knows how the fuel gauge on the 2ltr works? probably it is the same on many other cars?
My fuel gauge was reading very low (about half or less of what it should). It thas 3 connectors. One is ground, one connected to the fuel tank sender and one is +12V (my car is on negative earth). I removed the gauge, because the fuel tank sender resistance seemed reasonable.
I removed the gauge from my MGA to compare. The one from the MG is like described well on the internet (http://mgaguru.com/mgtech/electric/fg_01.htm): it has 2 coils: one called the "full" coil, one called the "empty" coil, both are connected on one point which is connected to the resistor on the fuel tank. The other ends are connected to ground and 12V. Measuring the resistance between the 3 connections gave 100 Ohm, 100 Ohm and 200 Ohm which makes sense (1 coil, the other coil and both together).
The gauge from the Lagonda is different: it has 180 Ohm between all 3 points. (how does this work with 2 coils, may be the upper one has a connection in the middle too). When I connect the gauge to ground and +12V, I could get it showing half full. Connecting the third to either ground or 12V would let it show empty or full. But that is not what the fuel tank sender delivers. The fuel tank sender connects more or less to ground only. On my gauge this leads to a value between empty and less than half full.
I opened the gauge (glas removed, face removed), see picture. I do not understand how it works, nothing seems broken, no possibility to adjust and however I connect it it does not do what it should. Was it made for a different type of fuel tank sender?
The only solution I see so far would be to buy a "normal" one (e.g. MGA) and put the face of the Lagonda instrument in.
Attachments: