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1. 06:42 AM - Interesting Carb temp anomaly (Alec Myers)
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| Subject: | Interesting Carb temp anomaly |
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 its original value (about 20C 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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