Need guidance on why my fuel gauge got scorched

[RoyKing]

I would leave the temp unplugged install a new fuse link, tank gauge and sender and see if they work. The temp sensor probably saw no excess current just shared the same voltage source. Can you find the wiring schematic online somewhere, if so post it that way I won't be guessing. What I've found is that not everybody wires stuff the way we do. Working on a late 80's CNC machine Kitmura taught me that.

 

[MA1920]

My service manual covers the 1920 and 2120. The wiring diagram for the 2120 is color coded so I've been trying to match colors to the 1920 diagram. One thing is strange, the 1920 is a 4 cylinder but the diagram shows 3 glow plugs.

 

[RickB]

They probably developed the line art for a 1720 and borrowed it for the 1920.

 

[RoyKing]

Both circuits show the voltage source is shared with a headlight circuit, and then into the dash, without any diagrams of the dash. Both circuits show the temp sender is ground loop with supply from the dash. If the temp gauge fails to work You may have burned connections in dash panel. So a shorted fuel sender could have eaten the dash circuit

 

[MA1920]

Thank you for taking the time to analyze the wiring diagrams. I read your post several times while studying the schematics. When I get the new fuel sender, I'll install the new sender, fuel gauge and fusible link....and hope for the best.

If the fuel sender may be at the core of the two gauges failing, is there any way to determine if there was something to cause the sender to fail? Or did the sender just reach the end of its natural life?

Thank you.

 

[RoyKing]

It would be hard to say the failure cause. If you did repair for years and the part was marginal to poor you would have replaced a lot of them. Or if the tractor had a severe life. If the parts was bad you would find the replacement part often gets revised and fixed.

 

[smilinjak]

Zydeco was ygvv

I ordered a new fuel gauge and fusible link. I want to make sure there aren't any other issues going on that could affect the new parts. After work my son and I pulled the float and checked the resistance as it moved. We had one probe on the positive lead to the sensor and the other to a good ground. As the float was moved the resistance would increase for an instant then drop back to 0.11, which is where it started. As I'm typing, I think we might have been on too high a scale. Were we checking the sensor/float correctly? We'll recheck it with the meter on a lower scale. As always, I appreciate the help.
You check of the fuel sender is incorrect. You should be checking resistance between the two leads of the sender. There is no hot leader to the sender it varies the resistance to ground for the sender. Your ohm meter should be set on the lowest scale it has. As the float arm moves the reading should make the needle move. From the diagram it looks like circuit 05 a black wire is a common ground for most of the circuits. The big copper coil on the back of the gauge is a resistor that was crossed somewhere. The mystery is where.
Smilinjak

Bob

 

[MA1920]

We pulled the sender and rechecked it. Previously I had the meter on kilo-ohms. The reading with the sender from the empty position was 109 at full position 4. I can't find the specs for the sender so how do I know if the reading is within spec?

 

[smilinjak]

We pulled the sender and rechecked it. Previously I had the meter on kilo-ohms. The reading with the sender from the empty position was 109 at full position 4. I can't find the specs for the sender so how do I know if the reading is within spec?

The exact resistance value id not particularly important. Your main objective is to find and repair the crossed wire to the gauge. Visually check the wire looms looking for mouse damage. Are there any other circuits that don't work ?
If your test meter is a multi function meter make absolutely certain , check it twice, it is set for voltage. Hook up the battery and check the black wire going to the gauge for voltage. Have sender disconnected when you make this check. Check for voltage on both ends of the blackened copper resistor. There should be battery voltage on one end and very reduced voltage on the other. Can’t give a specific number.
Smilinjak

 

[MA1920]

The exact resistance value id not particularly important. Your main objective is to find and repair the crossed wire to the gauge. Visually check the wire looms looking for mouse damage. Are there any other circuits that don't work ?
If your test meter is a multi function meter make absolutely certain , check it twice, it is set for voltage. Hook up the battery and check the black wire going to the gauge for voltage. Have sender disconnected when you make this check. Check for voltage on both ends of the blackened copper resistor. There should be battery voltage on one end and very reduced voltage on the other. Can稚 give a specific number.
Smilinjak

The two items that don't work are the fuel and temp gauge. Only the fuel gauge showed evidence of electrical overload. Due to a family birthday party I won't have much time to work on it tomorrow. I'll update as I make progress. Thanks for the help.

Bob