Stock CHT temp probe

[xcrmckenna]

http://m.pilotshop.com/catalog/inpages/rochcht.php?clickkey=627493

 

Is this the stock probe for cylinder 3 on a 77' 201? Pretty sure mine is broke. The panel cht gauge has stopped working and the threaded shaft is just spinning. The jpi is still reading temp so I figure it's either the connection, stock gauge, wires.

 

 

 

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[carusoam]

Ignore this response.  It doesn't match the hardware in the photo....

 

Stock CHT probes are usually resident in a well on the cylinder.

This photo looks like a TC hiding under a spark plug...

Often the spark plug seal probes get damaged during maint.  Often the ship's gauge gets location swapped for the plug seal type TC...

Either way, get the piggy back style TC that goes under the well in place of the plug... the plug type TC had the worst location error.  The piggy back under the well hardware has less error.  They haven't invented a two TC in the same well type TC, yet...

Need more detail?

Best regards,

-a-

[ArtVandelay]

It may be, but check the numbers stamped on the side for exact model, btw it's a thermistor, a thermocouple (TC) has 2 wires.

 

[Guest]

7 hours ago, xcrmckenna said:

 

http://m.pilotshop.com/catalog/inpages/rochcht.php?clickkey=627493

 

Is this the stock probe for cylinder 3 on a 77' 201? Pretty sure mine is broke. The panel cht gauge has stopped working and the threaded shaft is just spinning. The jpi is still reading temp so I figure it's either the connection, stock gauge, wires.

 

 

 

Sent from my iPhone using Tapatalk

 

That is indeed the CHT probe, and the part number in your link is correct.

Clarence

[N201MKTurbo]

A little cheaper from Spruce.

http://www.aircraftspruce.com/catalog/inpages/rochcht.php?clickkey=4244

[xcrmckenna]

That is indeed the CHT probe, and the part number in your link is correct.
Clarence

And the threaded stud shouldn't move right?


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[N201MKTurbo]

It shouldn't. But I have seen them work fine with the stud spinning,

I have never taken one apart to see how they are built, so I don't know exactly what is going on in there.

[xcrmckenna]

It shouldn't. But I have seen them work fine with the stud spinning,
I have never taken one apart to see how they are built, so I don't know exactly what is going on in there.

There was some corrosion on the connector when I took it off. I cleaned it off but never started the plane up again to see if it made a difference. I'll do that before I order a new one.


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[carusoam]

Ignore this post, it doesn't match the hardware in the photo...

CHTs use thermocouples... changing voltage with temp.

OilTs use thermistors... changing resistance with temp.

You don't need to run the engine to see the CHT work.  It will just read the temp as it sits... essentially OAT.

Best regards,

-a-

[ArtVandelay]

There was some corrosion on the connector when I took it off. I cleaned it off but never started the plane up again to see if it made a difference. I'll do that before I order a new one.


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Just use a multimeter on it, the resistance at room temperature should be around 10-20K ohms and should be less as it warms up.

[Guest]

8 hours ago, xcrmckenna said:

And the threaded stud shouldn't move right?


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Generally not, but they will work with the stud loose.  Best bet is to hold the ring terminal while tightening the nut.

Clarence

[xcrmckenna]

Generally not, but they will work with the stud loose.  Best bet is to hold the ring terminal while tightening the nut.
Clarence

I'm not sure if I explained it right. The threaded stud acts like it's not connected to anything and you can just twist it inside the probe. If I could figure out how to post a video on here I would. But I'll check it with an ohm meter in a few and make sure it's working.


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[Guest]

Just now, xcrmckenna said:

I'm not sure if I explained it right. The threaded stud acts like it's not connected to anything and you can just twist it inside the probe. If I could figure out how to post a video on here I would. But I'll check it with an ohm meter in a few and make sure it's working.


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I've seem some work with the stud loose and seen others not work with it loose.  I have a sheet from Mooney which give the resistance values for various CHT readings.  You can put a decade resistance box in place of the probe and test the gauge.  The probe is a variable resistance to ground.

Clarence

 

 

[jetdriven]

If you use an ignition wrench you can hold the stud while torquing the nut.. A socket with no backup wrench trashes the 90$ probe. Oil temp sender same thing.  From experience. 

Edited August 29, 2017 by jetdriven

[xcrmckenna]

I just changed out my bottom plugs with fine wires, should I put the same anti-seize on the temp probe as the spark plugs? Or do I need it?


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[jetdriven]

nope, just screw it in.