The gauge is likely seized and this is common on these machines. You can usually get it freed up with some penetrating oil in the spindle of the gauge. Pull the instrument panel, and then remove as many screws as needed until you can get to the motor. Squirt some oil in and try to get it moving gently. It might take a few days to get it freed up.

 

I am having a similar problem with my 445 and again techie 1961 gives me a good idea of where to start.

 

Didn't have much luck with it being stuck. When I turn the key on the needle moves up a little and just stays there.

 

The meter is like a voltmeter, various voltages move the meter to the different locations.

I could not find a correct sending unit for my non-JD tractor,, so I bought a sending unit at the auto parts store, added a resistor (trial and error) and the meter works perfectly.

Can you test the meter with various voltages? :dunno:

 

If I know what voltages it runs at.

 

I did notice that at ambient temp I had 9v at my sensor. I measured with the wire plugged into it. Not that it matters though

 

I gather that the sensor the voltmeter was measuring was the glow plug sensor?

It would seem that that the glow plug sensor is a switch and that it either opens to ground or not and that the bulb sees 12 VDC all the time but current only flows and the bulb illuminates when the sensor goes to ground. From what I can determine, the part number for the Water Temperature Switch is CH15516.

By contrast, the temperature gauge sensor is not a switch, but a variable resistor. It appears to be called up as a Coolant Temperature Sensor, part # T110736 and is located on the not hose side of the water pump as you indicated in your picture.

I noted the 4 VDC reading but figured that would be a number more likely showing off the coolant temperature sensor and would be consistent with about a five to six volt maximum supply voltage off the temperature gauge.

I do not know if both your temperature sensors have the same thread size but I think the thread size for my coolant temperature sensor on my petrol 425 is metric M14 x 1.25. My part number is M117054.

It just seems to me that if the thread sizes of both your sensors were the same, it would be easy for the parts guys to get the sensors mixed up.

 

The link below is to a discussion re disassembly of the instrument cluster.

http://www.mytractorforum.com/12-jo...rum.com/12-john-deere-forum/765065-instrument-cluster-disassembly-jd-425-a.html

As a result of that thread, I am pleased to say that much to my surprise, both my coolant temperature and fuel gauge are now working.

The fuel gauge system suffered from two problems, a missing float on the sender unit located in the gas tank and the harder of the two problems to fix, a frozen needle in the instrument cluster. As mentioned in previous posts, this is the problem your temperature gauge may be suffering from.

The thawing procedure required a combination of thread release fluid and WD-40, plus a week of time "watering/soaking" the two stepper motors that rotate the needles; patience is the key it seems.

About the only progress you may observe during the soaking process is that the needles can be moved with decreasing force each day, (if they previously rotated at all). As it was, I did not think that I had succeeded with the fuel gauge needle as it was still heavy when I gave up so to speak.

Regarding disassembly, I did not remove the needles - bad idea I figure, and not necessary - you just undo as many screws as you can find on the rear of the instrument cluster and soon the glass face will fall off - be careful re breakage - and then you can squirt fluids all over everywhere but particularly into the two "cans" the needles attach to.

It is also an opportunity to replace bulbs so before you take all apart, determine if your two instrument cluster illumination bulbs are OK and if the charge and oil pressure light as well as the PTO light work. I think the diesel might also have a glow plug light or something similar.

Regarding the temperature gauge, the theory is that low resistance in the temperature sensor is high coolant temperature, hence grounding the spade that clips on to the temperature sensor should make the temperature needle move full hot - however I was reluctant to do that as shorting something to ground that I do not understand has not always had the best results.

As such, to get the needle to move full hot, I grounded one side of those old type wire wound rheostats and to the other side of the rheostat, connected the spade that would normally clip to the temperature sensor and rotated the knob from full resistance to decreasing resistance. To my surprise the temperature gauge needle moved in sympathy with the rheostat knob. That meant for me that at least the gauge and wiring to the gauge worked and that the soaking process had worked.

Also I determined that the max voltage that shows on the spade from the temperature gauge is about 6 volts; I note you were seeing 12 volts so the gauge internals on your 455 may be different from my 425 but I doubt it. The gauge is really a variation of an amp meter or voltmeter masquerading as a temperature meter. I think as such, while 12 volts may feed it, only about five to six volts exits and hence measures at the unattached sensor conductor spade.

Later on, I got to measuring resistance readings from my temperature sensor between ground and the sensor tab with nothing else connected.

The numbers were about as follows where the temperature is that of the engine metal near the temperature sensor as measured with one of those infrared heat guns:
30F ~6,000 ohms; 70F ~2,500 ohms; 85F ~1,700 ohms; 160F ~300 ohms.

I am thinking that your new sensor was at room temperature so the reading of 170 ohms puzzles me unless it was installed and connected back to the gauge. A number like 1,700 ohms would be more reasonable however.

Incidentally, maybe in the summer when working correctly, the needle moves up to say half scale, but at least here in the near Arctic, the needle tends just to move up only to the bottom of the green. These indications seem to be normal for the petrol engine units anyway.

Another link of interest:

http://www.mytractorforum.com/12-jo....com/12-john-deere-forum/753034-glass-gasket-replacement-4x5-gauge-cluster.html

 

Went back out to the garage and did a little more checking. Turns out there are two temp senders. One is for the cluster and the other must be for the glow plugs.

Temp sender for the cluster. When I ground out the wire going to this sender my temp gauge pegs to the red.

Sender for glow plugs. When I ground out the wire going to this sender the glow plug light comes on.

 

So when I asked the parts guy for the temp sender he gave me the one for the glow plugs, which is fine because it was bad anyhow. My glow plugs did turn on though before I replaced the sender. But I didn't think they cycled when the engine was warm.

 

bbyer
I rechecked my readings and I had 1.056 k ohms at about 80 deg coolant temp. Not sure where I got 170 ohms at.

 

That number sounds much better. I found that when I was taking my readings, they seemed all over the place in that with the engine off, a few minutes later, the numbers on the ohm meter were different, not by a factor of ten, but certainly different.

The main thing is direction - high temperature is low resistance and with lower temperatures, higher ohm readings.

I appreciate your update - bedtime now for me.

 

The sensors don't have the same tread size. They are totally different. The meter in the picture isn't hooked to anything. It was just laying there.

 

Installed the new water temp sensor and the gauge moves up when I turn the key on and never moves any higher. I plugged the wire into the sensor on the other side of the thermostat housing and the needle moves up to where i think I should be when it's warm. How are the wires supposed to be hooked up and where are other people's gauges running when at operating temp?

 

My 455 generally operates in the bottom half of the scale when fully warmed up, unless the grills are plugged with grass, then it will creep up into the other side.

 

Mine is in the bottom third of the gauge. You can also check the technical manual wiring drawings for hookups.

 

Could someone get me a picture of their thermostat housing?

 

You have the diesel and I have the petrol 425 so I do not know.

Below is a link to where I think you might find some information related to the various temperature sensors on your engine.

It appears the pictures and information depend upon the serial number of your tractor. The diesel appears to have a very different setup from the petrol models. My 425 only has a water temperature sensor that connects to the gauge. It appear the 445 has both the sensor for the gauge and a water temperature switch connected to I think an overtemp light as well.

I expect the diesel has much the same, the question however is which is which. On the 445, from the parts sketch provided, one can determine which is the switch location and which is the sender location. You might also beable to figure it out from the data per the link, or near that data sheet.


John Deere - Parts Catalog

 

Here's a couple pics of mine

 

Thanks for the pictures. If you compare our pictures you can see that our sensors are in opposite sides of the t-stat housing. So my orange/white wire was going to the larger sensor and my orange wire was going to the smaller one. If I switch the wires around the gauge works. I'll have to try and swap the sensors around.

 

If one can swap places for the sensors, that would then suggest that the threads on both sensors are the same. I guess the electrical connectors are similar so perhaps the threads are as well.

It makes for a simple solution anyway.

I think the thread size for my single coolant temperature sensor on my petrol 425 is metric M14 x 1.25 and the electrical connector was a flat spade type. My part number was M117054 and it was located on the left side cylinder head per below.

 

I tried to swap the sensors and they are different size threads. I just don't understand how this ended up this way.

 

I suppose the wire for one of the sensors is long enough to stretch over to the far side and connect but the other is not. Even it both did, or you made up a temporary extension, you still would not get what I would call the desired results on the respective light or gauge.

About all I can suggest is take both sensors out and print those two pictures of yours and then take them to your JD dealer and hopefully he has in stock the two sensors deemed correct and compare them with what you already have.

I think you already did purchase one of them new but sometimes part numbers and bags get mixed up at the factory.

I have had that happen with Land Rover parts - rare, but it does happen.

With your diesel, I would think your temperature sender is what I would call a variable resistance sensor, (same as the petrol engine units), and the glow plug bulb related sensor, a switch.

I reread your 05-16-2015 -10:37 post and it basically says that your temperature gauge is working as it should, (sensor lead to ground and temp gauge shows full hot). When the glow plug sensor is grounded, the glow plug light illuminates as it should. That means you have the respective leads identified correctly and that they work also.

The sensor you purchased is I gather the glow plug sensor and it should be a switch I would think - that is depending upon temperature, it either goes to ground or it does not. I would think however that it would only be at ground when the engine was cold as I assume the light means the glow plug circuit has to be activated and held for some time? If so, then when cold the switch would be closed, (to ground). If the temperature gauge lead were connected, the temperature gauge should peg full hot. Then when the engine warms up a bit, the temperature gauge should show full cold as the switch would have opened and the ground condition eliminated.

It gets really interesting if the glow plug light is attached to a variable resistor sensor. Cold the light would probably be off or very dim and as the engine warmed up, the light would get brighter as the resistance within the sensor decreased allowing current to flow thru the bulb filament. What I do not know however is just what sort of a amp limit there is within a variable resistance sensor. The current draw on 12 volt 5 watt indicator bulbs can be perhaps 0.4 amps and I think that is quite a bit for a sensor to handle.

It is looking like your sensor problems are a lot tougher to resolve than the fuel pump? concern I am presently pursuing on my 425.

The good news is that in spite of the concerns, both our tractors are still operational.

 

Read post below

 

Did some reading in the tech manual. The coolant temp switch is used to shut the pto off if the coolant temp reaches 230* F.

 

I found this in the manual also and it shows the switch and sensor location as opposite of what I have. So I went out to the garage and removed them both and tried to switch them around again. Guess what they both threaded in the correct spots. Not sure what I did wrong last time I tried that. I'm glad I got it fixed but boy do I feel dumb now. I guess on positive is I now know what it means if my glow plug light turns on during operation.

 

I must say thank you to CAW455 for the pictures and bbyer for being persistent on swapping the switch and sensor haha