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  #1  
Old 04-09-2018, 09:05 PM
ben barron ben barron is offline
 
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Location: Fall City, WA
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Default erratic CHTL

In the last 15 minutes of a 2 hour flight the CHTL started jumping between 147 and 0 erratically. The CHTR was stable at 181 and EGTL/R at 1360, Any ideas?
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  #2  
Old 04-09-2018, 09:27 PM
DHeal DHeal is offline
 
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Most likely a loose or corroded wire or connection. Wiggle the CHTL sensor connection (under left front cylinder head) to see if you can duplicate the erratic reading.
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  #3  
Old 04-10-2018, 04:58 AM
BigJohn BigJohn is offline
 
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Clean up the connectors and spray with a contact cleaner. I have some at the hangar, I think the name of it is something like Deox-It.
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  #4  
Old 04-20-2018, 10:57 PM
ben barron ben barron is offline
 
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I tried all the above to no success. In testing today I discovered the erratic reading even with the engine off so there was nothing vibrating to jiggle a loose connection. Any other ideas?
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  #5  
Old Yesterday, 01:46 AM
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Piper J3 Piper J3 is offline
 
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Certainly sounds like a bad thermocouple. My EGT thermocouple failed in this exact mode. One source for the new part is... https://www.ebay.com/itm/Rotax-912-9...VXPF30&vxp=mtr
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  #6  
Old Yesterday, 04:29 AM
BigJohn BigJohn is offline
 
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Quote:
Originally Posted by ben barron View Post
I tried all the above to no success. In testing today I discovered the erratic reading even with the engine off so there was nothing vibrating to jiggle a loose connection. Any other ideas?
Swap L and R and see if trouble follows the part.
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  #7  
Old Yesterday, 07:02 AM
AirHound AirHound is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Certainly sounds like a bad thermocouple. My EGT thermocouple failed in this exact mode. One source for the new part is... https://www.ebay.com/itm/Rotax-912-9...VXPF30&vxp=mtr
Thank you for info. Another small issue ?
When sitting engine off the left indicates 20 higher. When operating both gauges come close? Any ideas as to why?
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  #8  
Old Yesterday, 06:42 PM
ben barron ben barron is offline
 
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Thanks for the tips, now before i remove it to cross check....How would i find the torque of the thermocouple (i tried to find it in the Rotax installation and maintained electrical manuals but have not been successful )?
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  #9  
Old Yesterday, 07:25 PM
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Piper J3 Piper J3 is offline
 
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For a quick trial leave thermocouples in place and switch the wires. Perhaps use alligator test leads to temporarily span wires from one side of engine to the other. Donít think Iíd fire up the engine but this might be a good static test to isolate if one thermocouple is bad.

Alligator test leadsÖ
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