1975 4000 SU temp gauge

wels

Member
Ok, I have been doing some trouble shooting my gauge cluster, actually I have two; a new one '76+ counterclockwise (ccw) and a model correct, clockwise, (cw) one. I also have a new jacket water thermocouple, the old one had the blade connection broke off. With the new thermocouple, on both gauge clusters, the temp gauge needles don't get much movement. At 212F neither needle goes past halfway on the temp gauge.

See pics - black lines depict where the needle was at approx 212F

Seems odd because the big CAT engines I work on alarm at 204F and shutdown at 212F.

Anyone know what temp should puts the needle into the red? Once I get the red line temp I think I will put in a resister to make the gauge max out correctly.

Thanks guys
Wels
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I suspect you have the wrong temp sensor, or else the one you have is faulty.

Also, keep in mind that these Fords are sleeveless engines. At 212 degrees, these Fords aren't even sweating yet. On the later versions of these same engines, on tractors with the digital dash, Ford set the alarm point at 250 degrees.

Finally, I'm not sure what size Cat engines you're working on, but a C15 won't shut down at 212. I just went into Cat ET and took a look - shutdown is at 223 degrees.
 

Bern

I work on Cats from little c 4.4 generators to 3608 but primarily c 18,32 and 3516

I am a merchant marine engineer. I was guessing on the alarms and water temps, but I thought I w close close. I guess I was off a bit.
 

I did more testing today.

I was able to scrounge up the old sending unit and file down the insulator so I could get a gator clip on it.

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Then I did a test with the old sending unit. At 212f the needle is almost in the red which is what I figured I would see. Not in the red but up there to let me know it's nice and warm.



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Looks like I need to get another sending unit. Hopefully the new one will work correctly.
 

Because I like to know why things work the way they do, I did a comparison between then the two sending units. The old unit had a resistance of 80 ohms at 185f and 45 ohms at 212f. The new sending unit had a resistance of 114 ohms at 185f and 88 ohms at 212f. From my gauge test results 43 ohms makes quite the difference on the readout.

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One more thing I did figure out while playing with the gauge clusters.

On the (cw) '68-75 cluster the sending units for both the temp sensor and fuel level sensor plugs into the outer blades.

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On the (ccw) '76+ cluster the fuel sender plugs into the outside but the temp sender needs to plug into the inner blade because of the way the resister and coil is set up on the temp gauge.


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Just figured that could be helpful for anyone updating the gauge clusters.

Wels
 
You definitely found the problem! I do know that the NH parts catalog has had quite the issue in the past years with correct temp sending units. Make sure the sending unit you are ordering is for a 1965 tractor.

One more thought - take an ohm reading of the old sending unit at room temperature, then compare with the new one before you leave the dealership. Better yet, have them test it to save you a wasted trip.
 
The cluster you have is an A&I retro cluster for a thousand series tractor except it has the CCW tach for the updated drive of the x600
series tractors. NH, for their part, never supplied that particular cluster in service. So what you have is a f*** up. I've installed a
couple of them as well. Basically, what Bern has told you is correct. Use the original sender for the tractor. You would not expect a Stewart
Werner type cluster to work with the AC style senders... but it does. Just go with it and don't think about it too much...

Rod
 

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