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CHT reading fluctuates and then dies

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Hello all
My left CHT first fluctuates and then drops to low end of range after 10-20 minutes of flight.
I am assuming the CHT probe is probably u/s. Can anyone assist with the part # and a place to purchase
the CHT for a CTLS, Dynon 180 EMS and Rotax of course.
Many thanks


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Sorry I can't read evidently.


First thing is these almost never go bad and the usual cause is a bad connection at the sender or in the 37 pin connector on the D120. The connection at the probe should be firm on the connection and not floppy. The second place these go bad is in the D120 37 pin connector on the back of the D120. There is a 1.2K resistor and sometimes this contact inside the plug breaks. It's and easy fix.

Check these two places first before buying a new sender. One way to test the probe is jump across the engine with a wire to the other probe and see if the problem follows the wire or if it really is the probe.

The CHT probes are VDO. Rotax wants an arm and a leg for them.

Buy them for a fraction of the price on Egauges.com. About $12

Under VDO temperature senders.

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Hello Roger
Very timely and useful practical knowledge ! It is encouraging to know the CHT probe is rarely the cause.
Many thanks indeed !

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