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CHT

 
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Snazpappy



Joined: 01 Jan 2019
Posts: 33
PostPosted: Sat Jul 08, 2023 5:41 pm    Post subject: CHT Reply with quote
I have a Yak 52 TW. The CHT in the back cockpit is mostly inop indicating zero. After engine startup I noticed the CHT in the rear cockpit would indicate normally up through about 200 degrees then the gauge would appear to fail and indicate bottom of the scale. I did a little troubleshooting today and put both CHT probes in my dewalt heat gun which can be set in 50 degree increments. Both gauges read normal up to about 200 degrees F. When the heat was increased beyond 200 degrees, the rear gauge appeared to fail and the front gauge read normally. I decided to isolate the rear CHT probe so I put just one probe in the heat gun to find which was the rear and found the rear gauge continued working when it was isolated but would read 50-100 degrees lower then the set heat, when set above 200 degrees, but the gauge continued to function. I then tried to put the front probe back in the gun, with the rear probe and as soon as I put the two probes together the rear gauge again appeared to fail.

Both CHT thermocouple are pancaked together and put on the same spark plug on the back of the engine. I have decided for now to replace both thermocouples to see if this fixes the problem, not sure what the problem may be, and was wondering if anyone has any ideas why my gauges are acting this way. I checked the wiring diagram and both thermocouples are totally isolated from each other other than be pancaked on the same plug. Both thermocouple s wiring are running through their own protective sleeves.

Any ideas or suggestions are appreciated.

Thanks

Todd

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dsavarese0812(at)bellsout
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PostPosted: Sun Jul 09, 2023 4:00 am    Post subject: CHT Reply with quote
Split the CHT probes between cylinders 3 & 4. With both probes on the same spark plug, the spark plug firing tip is significantly pulled out of the combustion chamber. Also, regardless of whether you’re using a Russian/Chinese or automotive spark plug, the plug with the CHT prob should not have a washer on it as that exasperates the issue just mentioned.
Dennis

Sent from my iPhone

Quote:
On Jul 8, 2023, at 9:42 PM, Snazpappy <snazman1(at)hotmail.com> wrote:



I have a Yak 52 TW. The CHT in the back cockpit is mostly inop indicating zero. After engine startup I noticed the CHT in the rear cockpit would indicate normally up through about 200 degrees then the gauge would appear to fail and indicate bottom of the scale. I did a little troubleshooting today and put both CHT probes in my dewalt heat gun which can be set in 50 degree increments. Both gauges read normal up to about 200 degrees F. When the heat was increased beyond 200 degrees, the rear gauge appeared to fail and the front gauge read normally. I decided to isolate the rear CHT probe so I put just one probe in the heat gun to find which was the rear and found the rear gauge continued working when it was isolated but would read 50-100 degrees lower then the set heat, when set above 200 degrees, but the gauge continued to function. I then tried to put the front probe back in the gun, with the rear probe and as soon as I put the two probes together the rear gauge again!
appeared to fail.

Both CHT thermocouple are pancaked together and put on the same spark plug on the back of the engine. I have decided for now to replace both thermocouples to see if this fixes the problem, not sure what the problem may be, and was wondering if anyone has any ideas why my gauges are acting this way. I checked the wiring diagram and both thermocouples are totally isolated from each other other than be pancaked on the same plug. Both thermocouple s wiring are running through their own protective sleeves.

Any ideas or suggestions are appreciated.

Thanks

Todd




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http://forums.matronics.com/viewtopic.php?p=511077#511077











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markbitterlich(at)embarqm
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PostPosted: Sun Jul 09, 2023 9:12 am    Post subject: CHT Reply with quote
Hey Dennis!��

Besides correcting spark plug depth into the combustion chamber (an issue that should be immediately corrected of course), I'm going to go out on a limb and bet it will also cure his backseat CHT gage issue.�

Failing that, it can only be the thermocouple itself, or the connection where it splices into the standard wiring.�
Anyway, excellent as usual.�
Mark

-------- Original message --------
From: Anthony Savarese <dsavarese0812(at)bellsouth.net>
Date: 7/9/23 8:02 AM (GMT-05:00)
To: m14pengines-list(at)matronics.com
Subject: Re: M14PEngines-List: CHT

--> M14PEngines-List message posted by: Anthony Savarese <dsavarese0812(at)bellsouth.net>

Split the CHT probes between cylinders 3 & 4. With both probes on the same spark plug, the spark plug firing tip is significantly pulled out of the combustion chamber. Also, regardless of whether you’re using a Russian/Chinese or automotive spark plug, the plug with the CHT prob should not have a washer on it as that exasperates the issue just mentioned.
Dennis

Sent from my iPhone

Quote:
On Jul 8, 2023, at 9:42 PM, Snazpappy <snazman1(at)hotmail.com> wrote:

--> M14PEngines-List message posted by: "Snazpappy" <snazman1(at)hotmail.com>

I have a Yak 52 TW.� The CHT in the back cockpit is mostly inop indicating zero.� After engine startup I noticed the CHT in the rear cockpit would indicate normally up through about 200 degrees then the gauge would appear to fail and indicate bottom of the scale.� I did a little troubleshooting today and put both CHT probes in my dewalt heat gun which can be set in 50 degree increments.� Both gauges read normal up to about 200 degrees F.� When the heat was increased beyond 200 degrees, the rear gauge appeared to fail and the front gauge read normally.� I decided to isolate the rear CHT probe so I put just one probe in the heat gun to find which was the rear and found the rear gauge continued working when it was isolated but would read 50-100 degrees lower then the set heat, when set above 200 degrees, but the gauge continued to function.� I then tried to put the front probe back in the gun, with the rear probe and as soon as I put the two probes together the rear gauge aga!
in!

Quote:
� appeared to fail.�

Both CHT thermocouple are pancaked together and put on the same spark plug on the back of the engine.� I have decided for now to replace both thermocouples to see if this fixes the problem, not sure what the problem may be, and was wondering if anyone has any ideas why my gauges are acting this way.� I checked the wiring diagram and both thermocouples are totally isolated from each other other than be pancaked on the same plug.� Both thermocouple s wiring are running through their own protective sleeves.�

Any ideas or suggestions are appreciated.

Thanks

Todd




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=511077#511077











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