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

 

[rScotty]

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?

Lets back up a little bit here. Some things are not adding up.

The temperature gauge is composed of a sender, a single connecting wire, and the temperature gauge. Your cooling system does have a thermostat, but it is not connected to the temperature gauge, and I know of no way to measure the thermostat's reisistance....or if it even has a meaningful resistance.
So far, we are assuming that you meant to say "sender resistance" and just used the wrong term.
Can you attach a photo of the back of the gauge and of the sender?
rScotty

 

[Qmar]

Hey All,

Thanks for all the replies. I did a more through test on the weekend while i was patching up the driveway. I tested the sending unit cold, warm and hot and got resistance in range with the post above.

After screwing around with it for a week, driving it down a rough gravel road seemed to "fix" the problem, now the gauge is working. So am back to the bad wire/bad ground theory.

Based on the wiring diagram it seems the dash shares a common ground for all the gauges and functions and I haven't seen any other issues with the other devices so its either the circuit board or the wire. If/when it happens again I will bypass the wire and see if that fixes it. If not its in the gauge cluster.

As one poster above mentioned it might be the screws in the back of the PCB board. I made sure they were tight but i might pull them out and clean them and see if that does the trick.

Thanks again.

 

[rScotty]

Hey All,

Thanks for all the replies. I did a more through test on the weekend while i was patching up the driveway. I tested the sending unit cold, warm and hot and got resistance in range with the post above.

After screwing around with it for a week, driving it down a rough gravel road seemed to "fix" the problem, now the gauge is working. So am back to the bad wire/bad ground theory.

Based on the wiring diagram it seems the dash shares a common ground for all the gauges and functions and I haven't seen any other issues with the other devices so its either the circuit board or the wire. If/when it happens again I will bypass the wire and see if that fixes it. If not its in the gauge cluster.

As one poster above mentioned it might be the screws in the back of the PCB board. I made sure they were tight but i might pull them out and clean them and see if that does the trick.

Thanks again.

Good plan. I noticed that the poster you are referring to - the one who fixed his by tightening the screws on the PCB - just happens to have the exact same make and model of tractor that you do. And he had the same problem. And fixed it. And even posted a photo.
You don't get much better advice than that.
rScotty

 

[rossn]

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....

View attachment 742728

I had a similar issue with my GC1705 gauge ceasing to work after many years. Screws were not fully snug but also not loose, per se. I removed, wire brushed screw and contact, and replaced/snugged (one-by one) and it works now. Thanks for the info.

 

[Mike1955]

All of the above suggestions appear to be written by some savy guys on this tech or computer stuff. The trouble must be either the sending unit, the cable going to the gauge or the gauge itself, which is a complete dash unit. So now swapping things is cheaper than taking it to dealer, and this is probably what they do. Sending unit is cheap so try that first if they have one. Or just put a old style on it in a different location. Good luck sir