Oil temp probe

[travis]

I have the EMS D-10 and have about 13 hours on my plane/dynons with great results.  However, today about 5 minutes into the flight the oil temp started swinging wildly.  As best I could tell it was swinging about 50 degrees F in both directions (up and and down) every 2 seconds or so.  Lets just say it got my attention!  The oil temps in cruise have always been rock solid; during normal cruise the temp varies by 1 or may be 2 degrees and is consistently always pretty much the same for the same power settings.  I knew the oil was not fluxuating 50 degrees +/- every 1 or 2 seconds, so I am thinking the probe must be bad.  As a side observation, the swinging seemed to be more at cruise power settings, in the pattern at very low power settings it was much less severe, and on the ground taxiing it was normal, sitting in the hangar it read steadily. Can you guys point me in the right direction???  I checked the wiring connection at the probe and it seemed solid and firmly connected.  I took it off to make sure everything was good and reconnected it. I'm thinking that it is a bad probe, and I am hoping it is covered by the Dynon warranty since it has about 13 hours of use before this!  Please let me know.

Travis

 

[dynonsupport]

Travis,
We'll be happy to replace the probe if that's it, but I doubt that the probe is bad. They are very basic probes and it would be very hard for them to fail in the way you mentioned. On top of that, I don't think we've ever seen one go bad.

The oil temp sensor is very, very sensitive to voltage changes. Because the oil temp uses the ground path from the engine to the rest of the airplane as the ground path, any changes in load from the alternator can cause a big change across this ground wire. We only need a few mV of change to see what you are seeing.

When it started acting up, is there any chance you had turned on some large load for the first time, like wig-wag lights, strobes, transponder, or ???. Maybe your battery was less charged than normal?

Whenever someone has issues with the oil temp, we always ask them to look over their engine ground. It needs to be big, free of paint, corrosion, powder coat, oil, whatever. Beyond that, the EMS needs to have a solid ground to the battery.

One easy-ish way to check all of this is to shed loads and figure out what is causing the fluctuation, and then you can also pull the alternator field in order to take the load off the engine ground. This should help you figure out where it is.

Please feel free to give us a call and we can talk to through it as well.

 

[travis]

I just went for another test flight after taking the connection apart, inspecting it, and putting it back.  The problem has now went away, or at least it did not come back during this flight of 45 minutes.  I don't remember just how snug the connector was before, if it was slightly loose would that cause the erratic readings?  So far all I can come up with is that it may have been loose, otherwise the ground to the engine is in perfect condition and I have never had any electrical problems otherwise.

Travis