Erratic Oil Temp Indication

Dynon101

I love flying!<br />
Joined
Mar 5, 2016
Messages
382
Can someone PLEASE help me determine why the oil temp indication on my airplane is so erratic?

Here is a picture of the Savvy chart of cruise and descent with the oil temp in blue and the GPS Altitude in yellow.

During this cruise phase of flight the engine was kept at a steady power and RPM however the oil temp indication was all over the scale.

This engine has been rebuilt about 20 hours ago and in the prior installation the oil temp was rock solid. Other than the engine having been rebuilt all of the wiring is the same as previous. When the engine came back the original oil temp sensor was missing so I replaced it with a new Dynon oil temp sensor PN 100409-001 and that is when I noticed the erratic reading. I then replaced the oil temp sensor with the same part number and it is still very erratic.

For testing purposes I have taped some digital thermocouple probes to the engine to oil cooler outlet pipe and a second one to the oil cooler to engine inlet pipe and the digital thermocouple readings are very steady so I have confirmed that there is nothing odd going on inside the engine so this must be a bad sensor reading.

All of the other EMS readings of pressure and CHT/EGT temps are solid and it is just the oil temp that is erratic.

The engine is a Lycoming and the oil temp probe is inserted into the oil filter adapter housing real close to the Vernatherm where the other oil temp sensor was installed.

Has anyone else had this issue???

THANKS!!!
 

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djones

Administrator
Staff member
Joined
Jul 19, 2010
Messages
267
I have seen this before on Lycomings. I would suggest running a ground wire to the oil filter adapter. I have seen them not grounded well due to the gasket and sealers preventing the adapter from grounding through the engine case. Make sure the engine ground itself is good.
 

Bud_Keil

Member
Joined
Apr 9, 2013
Messages
44
Location
Shell Knob, MO
I just resolved my erratic oil temp indication issue on my D10 EMS. My temp indication seemed to be reading accurately up thru 200 degrees but then went wild. A new Vernatherm, a new single wire temp sensor, flushing the oil cooler, new cowl baffling, and changing the engine grounding scheme didn’t solve anything. A two wire sending unit thats grounded back thru the instrument ground has me flying.
 
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