Kubota 3240D temperature gauge showing 5 bars when cold.

[jim.grove1]

I have a Kubota 3240D that the temperature gauge is not working properly.
It shows 5 bars when cold as soon as the key is turned on.
I have replaced the temperature sensor just below the thermostat and it did not change.
As soon as the tractor starts to warm up I get a message that it is overheating.
Any suggestions on where to look for the problem?

 

[PoTreeBoy]

I have a Kubota 3240D that the temperature gauge is not working properly.
It shows 5 bars when cold as soon as the key is turned on.
I have replaced the temperature sensor just below the thermostat and it did not change.
As soon as the tractor starts to warm up I get a message that it is overheating.
Any suggestions on where to look for the problem?

Probably a short to ground between the gauge and the sensor.

 

[North Idaho Wolfman]

This is the sensor you changed?

Pull the instrument cluster and check these 2 connections.
Then while it's out check ohm's on white wire with sensor disconnected.

 

[jim.grove1]

Yes that is the sensor I changed.
Any advice on how to pull the instrument cluster?
What should the white wire ohms be?
Also when I had the sensor disconnected the temperature gauge still read 5 bars.

 

[North Idaho Wolfman]

Check the envelope top right.
The ohms should be infinite.

 

[jim.grove1]

Took me a while to get to testing.
White wire with sensor disconnected = infinity
White wire with sensor connected = 9.90 k ohms - in garage at room temperature
Ground wire with sensor connected = 7.85 k ohms
Other information: got same readings by testing pins on back of panel
Back of panel Pin 8 Power Supply 12V (from battery) - 12.6V
I went into diagnostic mode. T2 coolant temperature sensor voltage = 1.071 V
values from service manual 140 F (2.80 to 3.00) 212 F (.77 to .83) so 1.071 would be close to 200 F which is about what the gauge is reading.
T4 Battery Voltage is showing .561 V no where near correct although it is correct at the pin on the back of the panel.

Also I have to change the angle of the panel or put pressure on the B plug wires to get the panel to show the display. Power is on pin on back of panel and display lights up, but no words show without moving panel or wire bundle.
I tried to look for loose wires in the plug connector by placing a small wire in each connector and then flexing the wire bundle. I saw no change in the meter reading when looking at ohms or volts so I don't think the loss of display is the wire bundle.
I am guessing the display panel my be defective. Pulled circuit board and saw nothing obvious.

Please give me your thoughts. Anything else I should check?

 

[jim.grove1]

Another question.
Is there a way to repair the connector on the wire bundle if I find that a loose wire is the problem?

 

[GreensvilleJay]

this...
put pressure on the B plug wires to get the panel to show

sounds like the connector isn't properly soldered to the PCB. Common failure as big pins need more heat for wave solder to flow compared to itty bitty SMT chips and things.

best to remove display unit, inspect on workbench, resolder every one of the 16 pins.
Actual 'time to repair' ( the soldering) is less than me typing this message out......

 

[North Idaho Wolfman]

Another question.
Is there a way to repair the connector on the wire bundle if I find that a loose wire is the problem?

Yea what he said!

 

[jim.grove1]

this...
put pressure on the B plug wires to get the panel to show

sounds like the connector isn't properly soldered to the PCB. Common failure as big pins need more heat for wave solder to flow compared to itty bitty SMT chips and things.

best to remove display unit, inspect on workbench, resolder every one of the 16 pins.
Actual 'time to repair' ( the soldering) is less than me typing this message out......

Showing my ignorance. What equipment do I need to resolder the pins? Do I add solder or just reheat? If adding solder what should I use. I am willing to try but need some instruction. I have soldered copper pipes and large wires, but never connections on a circuit board.