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erratic CHTL

ben barron

Well Known Member
Patron
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?
 
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.
 
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.
 
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?
 
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.
 
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 )?
 
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. Don?t think I?d fire up the engine but this might be a good static test to isolate if one thermocouple is bad.

Alligator test leads?
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CHT install torque?

Thanks for all the help.

I wanted to confirm the torque to replace the CHT in my RV12 with Rotax 912 ULS. Would it be the same as the oil pressure sensor? I could not find a similar chart for the CHT in the Rotax manuals, the Installation Manual (page 148 of 203) shows oil pressure sensor torque at 133 in. Lbs.
 
Last edited:
Torque alert!

Ben, 133 in-lb is too much, like twice as much. Be careful, you don't want to strip anything out of that alum head.:eek:
A lot of torque values are found in the Illustrated Parts Catalog. I see the CHT sensor torque as 62 in-lb.

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The B indicates Loctite 243 for the threads. I don't guarantee my research, please independently confirm.
 
The bolt and nut torques that used to be in the Parts manual are all now in the new edition Heavy Maint. manual.
 
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