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Old 06-28-2017, 07:30 PM   #1
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Thermistor

Hi All,
What does the thermistor do on the aftercooler of my Cummins? I have a 6BTA with turbocharger. Looked at the wiring diagram and can't figure it out. I think it shuts down the turbo when it detects high temps in the aftercooler.

Thanks!
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Old 06-28-2017, 08:25 PM   #2
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The thermistor senses the intake manifold temperature and is part of the Air Heater control. Below certain temperatures and engine rpms, the air heater grids are energized to pre-heat the intake air, reducing smoke and allowing the engine to run smoothly.

In warmer climates, these are often disabled or even removed because the heaters create a heavy load on the alternators, and are thought by some to shorten their lives.

Here is a schematic for your reference.
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Old 06-28-2017, 08:39 PM   #3
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Rats, I thought this was going to be a thread about the thermistor in the refrigerator. Our freezer is colder than Fairbanks in January but the fridge below is lukewarm. An RV'er told me that's a classic thermistor issue. I open the doors though and can't find anything that looks like a thermistor, just a thick black wire on a freezer shelf.
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Old 06-28-2017, 09:50 PM   #4
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Warning - thread drift!

Thermostat maybe, but thermistor? Naaah.
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Old 06-28-2017, 10:05 PM   #5
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Actually some rv fridges use a thermister as the sensor. It is often run on the top shelf OR to the cooling fins .
That thin black wire is the thermister. They also have to be located in the right place. Maybe it has fallen or otherwise moved from the original location.
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Old 06-28-2017, 11:14 PM   #6
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Poop! None of my fridges have had thermistors therefore nobody has a fridge with a thermistor...isn't that how it works?

Rats. I guess I'll go watch Netflix - good night boaters!
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Old 06-29-2017, 12:18 AM   #7
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A thermistor is simply a resistor that changes the resistance based on the temperature.

Many fluke and other VOM's include a thermistor mode where it turns the VOM into a temp sensor by converting the resistance into degrees temperature.

It often looks like a wire, or actually two wires, since you need a completed circuit. On an engine, a thermistor can have one wire since the block is the ground and the other half of the circuit.

In the fridge, it will probably have a jacketed wire with two conductors that will go back to the temp controller.

If the fridge "black wire" is very stiff and does not appear to be insulated, it is probably an old style capillary sensor that goes back to a thermostat. Those cannot be kinked or it will seal off the capillary and stop the pressure from getting from the sensing tip back to the thermostat. Here is an example of the fridge one...

https://www.zoro.com/ranco-refrigera...Q&gclsrc=aw.ds
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Old 06-29-2017, 07:01 AM   #8
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Quote:
Originally Posted by LarryM View Post
The thermistor senses the intake manifold temperature and is part of the Air Heater control. Below certain temperatures and engine rpms, the air heater grids are energized to pre-heat the intake air, reducing smoke and allowing the engine to run smoothly.

In warmer climates, these are often disabled or even removed because the heaters create a heavy load on the alternators, and are thought by some to shorten their lives.

Here is a schematic for your reference.
Interesting that there are 2 seperate heater circuits.
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