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12-23-2019, 09:11 AM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,514
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Quote:
Originally Posted by RV74ME
I confirmed that the wires were reversed at dsub (lo was hi, hi was lo)
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Well, good you got to the solution.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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12-23-2019, 10:19 AM
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Join Date: Dec 2015
Location: Auburn, AL
Posts: 200
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Quote:
Originally Posted by snopercod
Water boils at 210.5 F at that altitude, so no big deal. I'm not convinced that you found the problem, though. If the wires were reversed, you would be sending negative voltage to the box and get the big red X again. Maybe they're reversed at the box and somewhere else, too?
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Guess i should clarify. I knew back when i did first engine run that the dsub was wired backwards. I got the big red X?s. so instead of pulling all that apart, i took (what i thought) would be path of least resistance. So i hooked up red to yellow, yellow to red to the leads of the probe. This gave me temperature indications, but just not accurate. Didnt know how inaccurate it was until first flight
__________________
Steve T.
CFII/MEI/ATP 737,DC-10
RV-7 slow build
AUO
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12-23-2019, 11:00 AM
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Join Date: Jun 2005
Location: Georgetown, TX
Posts: 326
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Quote:
Originally Posted by RV74ME
Guess i should clarify. I knew back when i did first engine run that the dsub was wired backwards. I got the big red X’s. so instead of pulling all that apart, i took (what i thought) would be path of least resistance. So i hooked up red to yellow, yellow to red to the leads of the probe. This gave me temperature indications, but just not accurate. Didnt know how inaccurate it was until first flight
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"Least resistance"
Given the wire type differences and resistance down the length, probably gave you the most resistance 
__________________
Brian Decker
Retired Firmware Guy and Airplane Builder
2020 RV-14 QB -- Under construction - Tailcone & Empennage Complete.
2018 RV-7 QB -- Built, Flying
2007 RV-7 QB -- Built, Drowned, Resurrected and flying
1998 RV-8 QB -- Started, Sold
1986 Mooney 205SE
1980 Mooney 231
Aided and abetted building a number of other RV's.
Last edited by bjdecker : 12-23-2019 at 11:14 AM.
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12-23-2019, 04:03 PM
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Join Date: Aug 2016
Location: Asheville, NC
Posts: 2,092
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Quote:
Originally Posted by RV74ME
So i hooked up red to yellow, yellow to red to the leads of the probe.
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So what you had there was three thermocouples in series. One at the probe in cylinder head, another at the junction between the probe and lead wire, and a third at the D-sub connector. You do the math...
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