GC1715 Temp Gauges Failure

[Qmar]

Hi, I have a MF GC1715 and i'm having problems with the temperature gauges. I found a previous post about diagnosing the problems with either the wire or the sensor, but both seem to be working. I have a connection from the dash connector to the thermostat, and the thermostat changes resistance as the tractor heats up.

Is there a way to test the gauge? I tried shorting the thermostat to ground and did not see a response on the gauge. I imagine I would have to replace the entire cluster which would be $$$ so i want to be sure.

Any ideas?

 

[Roadworthy]

Welcome to TBN. If you can isolate which wires feed the gauge you can try feeding it a low voltage - five volts or less. If the needle is going to move that should move it. Depending on the electrical system that could put you at half scale or full scale. Even with a twelve volt electrical system some instruments may run at five volts. If you can locate a schematic that would certainly help.

 

[kenmbz]

If you can measure the resistance to between the gauge and ground while disconnected from the sender, that should tell you something about the gauge itself..
Some people had issues with grounds getting loose or dirty making the temp gauge stop working.

And welcome to TBN!

To check the sender is in spec:

 

[Qmar]

Well I ran out there on lunch, I hooked up my power supply and connected the -ve to the battery ground and positive to the wire which I removed from the Thermostat. Dialed it up or 5v with the tractor in "on" and there was no response on the gauge.

Tested the thermostat terminal to the thermostat housing and got 400 Ohms.
Tested the Gauge end of the wire to the thermostat housing and got 400 Ohms.

Kenmbz is that chart for this particular tractor?

Tractor is sitting in a heated shop around 10C.

Wiring diagram shows a wire running straight form the gauge to the sending unit., I've checked out all the fuses as well and they test ok.

thanks for the help.

 

[kenmbz]

It was for a GC1723 I think. Should be close to ours.

 

[WranglerX]

Had a temperature gauge failure on my NEW GC 1715 tractor on arrival..... Found out the 3 screws that attach the printed circuit board to back of temp gauge were loose.... Check the screws for snugness....

 

[rScotty]

Well I ran out there on lunch, I hooked up my power supply and connected the -ve to the battery ground and positive to the wire which I removed from the Thermostat. Dialed it up or 5v with the tractor in "on" and there was no response on the gauge.

Tested the thermostat terminal to the thermostat housing and got 400 Ohms.
Tested the Gauge end of the wire to the thermostat housing and got 400 Ohms.

Kenmbz is that chart for this particular tractor?

Tractor is sitting in a heated shop around 10C.

Wiring diagram shows a wire running straight form the gauge to the sending unit., I've checked out all the fuses as well and they test ok.

thanks for the help.

I wouldn't expect that there would necessarily be a response from the gauge hooked up that way.

In old style hookups in the pre-digital age, the positive voltage goes through the gauge and then to the variable resistance of the sender that lives in a pocket in the engine block close to the thermostat. The circuit is completed because one side of the sender is grounded through its case.

In several digital temperature gauges I've traced, the digital display is a 5 volt display that is driven to display the lowest temperature when it sees a full 5 volts from the engine's fuel computer. The computer varies the voltage output to the temperature digital readout depending on the resistance it reads in the temperature sensor. 5 volts gives a full cold digital reading and 0 volts gives a full hot display and over-temperature alarms.

All common rail diesels have engine computers, and so do some of the separate injection type as well. I don't know if your Iseki diesel has an engine computer but it seems likely.

What this means is that if you have a bad connection or broken wire between the fuel computer and the digital temperature gauge, it will report a falsely high engine temperature.

Just like DL says in the message above, that's also the first place I would look...for a bad ground or bad connection between the computer module and the display.

rScotty

 

[WranglerX]

I wouldn't expect that there would necessarily be a response from the gauge hooked up that way.

In old style hookups in the pre-digital age, the positive voltage goes through the gauge and then to the variable resistance of the sender that lives in a pocket in the engine block close to the thermostat. The circuit is completed because one side of the sender is grounded through its case.

In several digital temperature gauges I've traced, the digital display is a 5 volt display that is driven to display the lowest temperature when it sees a full 5 volts from the engine's fuel computer. The computer varies the voltage output to the temperature digital readout depending on the resistance it reads in the temperature sensor. 5 volts gives a full cold digital reading and 0 volts gives a full hot display and over-temperature alarms.

All common rail diesels have engine computers, and so do some of the separate injection type as well. I don't know if your Iseki diesel has an engine computer but it seems likely.

What this means is that if you have a bad connection or broken wire between the fuel computer and the digital temperature gauge, it will report a falsely high engine temperature.

Just like DL says in the message above, that's also the first place I would look...for a bad ground or bad connection between the computer module and the display.

rScotty

The GC 1715 does not have a computer.....

Its a simple circuit that puts a "resistive ground" out from "water temperature sensor" (term used on wiring diagram) back to "U" terminal on a analog gauge at instrument panel and through gauge to +12 volts... For all practical purposes temp gauge is nothing more than a "voltmeter" in concept.....

 

[Roadworthy]

You're getting a lot of good suggestions. If you can access the circuit board check the solder connections. You are looking for cold solder joints and cracked or broken traces.

 

[WranglerX]

Believe temp gage is a analogue unit...Balance-coil or magnetic temperature gauge.

Temperature Indicators (Automobile)

12.6. Temperature Indicators Temperature indicators are used to indicate the driver regarding overheating or an abnormal condition of the cooling system. For this purpose, a temperature indicating light and/or gauge is installed in the instrument panel of the car. Both […]

what-when-how.com