X495 Temp sensor resistance

[oldnslo]

I am working on a 2002 X495 with Yanmar 3TNE74C engine where temp gauge is erratic. I have service manual for X749 and its shows temp sensor resistance should be 40 - 700 ohms. I looked at Deere parts and both models show using Temp sensor P/n T110736 so am I correct to presume the ohms should be the same for both models.

I am measuring 1375 ohms engine cold and 240 ohms engine at operating temp.

Getting 8.7 VDC in the sensor wire. I could not find where this voltage is mentioned in the service manual.

 

[Zebrafive]

Yes, OHMs should be the same for both sensors.
700 OHMs hot, 40 OHMs cold.
The wire should have 6-7 volts. This is from my x485 service manual, Electrical/ Instrument Panel Diagnosis

 

[oldnslo]

Thanks zebra 5

I ordered some 100 ohm resistors today and plan to use them to simulate the temp sensor to see if gauge reads stable. I am concerned could have parallel leak path in circuit board - instrument cluster causing gauge to be erratic. I figure resistors should provide consistent fixed load to eliminate one variable

 

[Amvcane]

Great idea with the resistors.
If you haven't done so already, make sure your signal wire from the sensor isn't shorting out intermittently on its way to the dash cluster.

 

[Zebrafive]

The gauge/instrument clusters in these tractor have given a lot of problems. If you are comfortable working on printed circuit boards (I am not) check the connector pins for cracked solder joints.

 

[oldnslo]

Zebra
I am much better with sledgehammers than circuit boards

appreciate the input on these clusters are a known problem.

 

[oldnslo]

Update on testing of temp gauge on the x495.
Per service manual 700 ohms is cold resistance on temp sensor and 40 ohms is at 212 degrees.
I installed fixed 300 ohm resistor between temp sensor wire and ground. Temp gauge needle was in the green approximately 1/8 inch.
200 ohm resistor gauge was approximately 1/3 - 1/2 way in green
100 ohm was 3/4 in green
50 ohm was approximately 1//2 into red zone.

driving around with 100 ohm gauge varied slightly on side hill but never once pegged red or dropped to cold

going to replace water pump since leaking out weep hole and install new temp sensor, thermostat and hoses since these are all appear to be original

will let you know how gauge operates with new temp sensor