alec(at)alecmyers.com Guest
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Posted: Mon Apr 10, 2023 5:42 am Post subject: Interesting Carb temp anomaly |
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Any suggestions about this strange behaviour…?
I have a TC aircraft with a Lycoming O-320 engine, and it has a Marvel Schebler MA4 carb, in which is installed a regular B-5 positive temperature co-efficient temperature probe, connected to an instrument on the panel.
When I switch on the instrument panel lighting in flight - the indicated carb temperature goes up - by typically 10° C.
When I switch the instrument lighting off again - the indicated carb temperature goes up again - by another 10° C.
It then seems to settle back down to it’s original value (about 20°C lower) over the next few minutes.
Some kind of grounding problem - instrument lighting circuit current being carried in the current loop for the temperature probe causing extra voltage drop somewhere - but why does the temperature go up even further when I shut off the instrument iighting?
Does anyone have a clue?
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