Oil Temp

Had a recent situation where I noticed my oil temp. seemed to be stuck at 150*F, (Superior 0-360) RV8A. Contacted Dynon and was told to check engine grounding, no change, Finally changed the Oil temp probe PN 100409-001 now I am seeing temps where they should be 190*F to 200*F range. Strange that the defective probe would work well until it hit 150* and then remain there, never changing even 1*

I am having the same problem with my dynon oil probe, oil temp only read max 150 F after 10 hour of Flight, I checked with a second temp probe and second one reade 185 F, just where it should be.

For what it's worth, if it is a grounding problem with the Dynon units you will more likely see HIGH temps rather than low. Too, if you turn off the alternator you will see the value change immediately - that is the biggest clue to ground problems.

breister said:

For what it's worth, if it is a grounding problem with the Dynon units you will more likely see HIGH temps rather than low. Too, if you turn off the alternator you will see the value change immediately - that is the biggest clue to ground problems.

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I have checked everything and I have tested the oil probe temp versus resistance from a chart sent by dynon and the problem is oil probe. So I need a new one.

Chalk up another one.

I cut a cross country flight short today when indicated oil temp would not get above 150F, it was not fluctuating. The engine is normally rock solid at 170F oil temp. It wasn’t like this yesterday. I checked the crimp to the sensor, checked the engine to sensor continuity, checked engine to batt ground, all no issue. Based on this thread and others, I’m going to replace the sensor, probably with the GRT two wire to end the case ground dependency. Other than shortcutting the diagnostics ( no pot of boiling water, etc), anyone have any other feedback? Can anyone point me to the reference info on resistance vs temp, in case I do go there? Thanks.

5/16 update: the plot thickens. At the airplane this morning. Confirmed case and sensor grounding again. Pulled sensor and ran it up to 190F in a water bath, using a k type TC in parallel as reference. I was expecting the OT sensor to stop changing at 150F but that didn’t happen. For reference, I was at 100 ohms at 190F. Charting it was what I expected based on ref data I could find. I pulled the D180 data, and it’s clear whatever happened happened yesterday in flight. When whatever happened happened, temp goes from 168F to 150F and stays there exactly until engine cool down, regardless of power setting. Using resistors from another project (all I had was a few 360 ohm 5W monsters) I was able to test the D180 response to different resistances, and that seems normal, I took it from 108F to to 195F based on 358 ohm to 72 ohm respectively, and a few points in between.

The two wire sensor is already on order, so I’ll continue down that path, but this could get more interesting.

5/22 update: changed sensor to GRT two wire, reconfigured Dynon, and all checked out, oil temps normal in the 165F to 180F range, consistent with light profile at the time. I went back into the EMS data for the last three flights (vs just the problem flight) and found a number of occasions where the OT quickly dropped from 175F-ish to 150F in 15 seconds or so, then it held there for as much as a half minute, then jumped right back to ‘normal’ in the next data entry (set for 5 sec data rate). Oil temp doesn’t mechanically jump 20F in five seconds. It seems like I caught an intermittent malfunctioning sensor early.

I’m happy to not have to mess with the thermo bypass valve!

Moral of the story? I’m not sure there is one. Use past data to bolster diagnostics, maybe? The malfunctioning sensor is still intermittent, but it showed up in the data. The other point....this was the last circa 2010 EMS sensor supplied by Dynon in my airplane. All the rest have been changed out with prior issues/diagnostics.