How to measure/ check torque converter oil temp sensor???

[Northeaster]

Hi Folks,

My brother in law has bought a used 580K, about 20 years old. The torque converter oil temp gauge goes to hot almost immediately, and the needle appears to have alot of shake to it.
Don't have a service manual for it yet. I would really appreciate it if someone could tell me how to measure something like the resistance, voltage, etc of the sensor, (and whether it needs to be measured while off, idling, etc) in order to see if it is a bad sensor, gauge, etc.

Any help woudl be appreciated!

 

[Craig Clayton]

I look after large electric water pumps ( like 2000 Horse Power ).
We measure the temperature of the bearings oil temperature with a probe called an R.T.D. . These are called resistance temperature detectors. They have a platinium winding core at 100 ohms. Lets say you apply 24VDC to the 3 wires that come off the detector and this is feed to a meter that reads this as temperature. If it gets hot settings in the reader set off alarms saying it is running hot.
You probably have the much cheaper version, it is called a thyristor it has a much higher resistance and uses only 2 wires. So I believe 12 VDC is applied to one wire and the other wire goes to the meter which is scaled to read the temperature of the oil.
With any detector the first thing is to work out is the temperature real ie the oil is too hot or the detector/ wiring / panel meter faulty.
I would suspect with the meter jumping the wiring is ok , the meter is reacting to a input. So this leaves the thyristor at the torgue converter . If you take the wire off the back of the panel meter it should go to zero ( I THINK ).
Lift the wire off and see if the tractor will run unless it is also connected to the shut down circuit.
This is the best I can do.

Craig Clayton

 

[Northeaster]

Hi Craig,

That is certainly a good place to start. Thanks for taking the time to explain how they work, in a very clear way!

 

[Northeaster]

After consulting a service manual, it says to unhook the wire from the sender. Then ground out the wire and if the gauge goes to high, the gauge is fine, and the sending unit is bad. This is exactly what happened, so I guess we will order a new sending unit.

While we are at it, the fuel gauge is not working either. Shows empty. despite lots of fuel in tank. Manual says to take wire of sending unit , ground out, and if gauge goes to empty, gauge is good, sender is bad. This is what happened, after the gauge initally read about 1/4 tank \9with wire disconnected) so it looks like another bad sender.