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Dynon D100/D120 Erratic Oil Temps

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PH-SCP

Well Known Member
Hello guys,

I am flying an RV-9 with a Dynon D100/D120 combination. Engine is a Lycoming O-320. EGT and CHT seem to fluctuate a little but what really bothers me is a dramatic increase in oil temperature whenever I switch on the lights of the plane. It's equipped with strobes, nav-lights, a landing light and a taxi light (yes... you can't miss it:)) and whenever I switch on any of these lights, the oil temperature rises. When coming in to land, fully lighted up on final, the oil temp goes out the roof, well above redline.
It's most likely a grounding thing but before I start working on it, I would really appreciate pointers in which direction to look..

Anyone out there with similar problems and how did you fix it ?
Thanks !!
 
Last edited:
99% of the time this is a grounding issue. It's the ground between your engine block and the loads in your plane. When you increase the load in your plane (the lights) then your alternator puts out more current. This current goes from the alternator to the engine block to whatever cable you have. When you have resistance in here, higher loads mean higher voltage drops, and this causes an error in the oil temp probe that shares the ground with the engine.

We've seen corroded mounting points, powdercoated mounting points, frayed cables, cables that are just to small, etc.
 
Thanks....

..... for the quick answer. Really appreciate that. The first thing I will look at is the grounding of the engine block.

Love this forum :)
 
I just experienced this last week, exact same symptoms. It was indeed a poor ground problem.

Larry
 
Allright... that's good news... I have a day off tomorrow and will look at the grounding issue.. Thanks a lot !
 
Note: The sensor itself sometimes does not achieve a good ground to the engine block, particularly if you (correctly) use thread sealer. Options are to use the GRT 2 wire sensor, or create a ground strap around the sensor using a hose clamp and run a ground wire to the block.
 
I had the day off today and went to the airport to work on the RV, disconnected the engine ground wire and cleaned both ends. There was no corrosion or paint or anything else that could have caused a bad grounding. Looked pretty clean and tidy. If weather allows, I will fly in the morning and let you all know what happens to the oil temps....

Thanks Breister for your comments. It looks like I'm heading the same way, may be a local grounding problem...

Thanks sofar... love this forum !:):)
 
So I cleaned the ground connection on both ends of the really sturdy and thick ground connection that run from the engine block to the firewall. Flew the plane and I see not much improvement. Whenever I flip on the lights, the oil temperature goes up sky high. :mad::mad:

Next thing I'll try is to run a ground cable from the probe itself and see if that cures the problem..

Also, EGT & CHT are not very stable, they fluctuate all the time and coming to think of it, MP does the same. Should I look in an other direction too:confused::confused:
 
Don't neglect to check the ground cable from the battery to the firewall and to the engine block itself. That's where my problem was, even though the starter etc worked fine.....

Larry
 
Find a REALLY GOOD....not just because you think they are but a REALLY good electronics guy to find your earth faults. There is a problem with grounding for sure!
 
Problem could also be caused by a poor or changing ground going to the DYNON unit. Just sounds like the ground potential of the sensors and the DYNON unit are not always the same. Might want to run a ground strap from you panel ground point to the FW if you have not already tried this.
 
PH-SCP said:
So I cleaned the ground connection on both ends of the really sturdy and thick ground connection that run from the engine block to the firewall. Flew the plane and I see not much improvement. Whenever I flip on the lights, the oil temperature goes up sky high. :mad::mad:

Next thing I'll try is to run a ground cable from the probe itself and see if that cures the problem..

Also, EGT & CHT are not very stable, they fluctuate all the time and coming to think of it, MP does the same. Should I look in an other direction too:confused::confused:
Click to expand...

Ok, you've given some strong cues here. Easy way to prove bad ground:

1. With engine running and oil temp on screen, turn alternator OFF. If the oil temp goes down, you have a bad ground somewhere between the alternator and the grounding point for your avionics.
2. IF you have an EFIS backup battery (this won't work without), next turn off the master switch. If the temp changes again you have a bad ground between the battery and either a) the avionics ground block; b) the engine block; c) both of these.

I bought an older plane, and went nuts trying to figure this out - all the connectors were clean and torqued very tight. Finally found that MY problem was caused by a combination of poor ground between sensor and engine block (added the ground strap) and also a poor crimp on the battery cable connectors (loose wire in the sleeve). Find someone with one of those giant crimping tools and cinch those suckers tight.
 
Thanks Breister ! Appreciate that. I will look at the points that you made and keep you all posted on how it's going !

:cool:
 
I was having a lot of problems with the Oil Temp reading on my Dynon D-180.

I installed the GRT 2 wire sensor today and now if functions perfectly.

Only $20.00 for the sensor and they even supply it with the copper crush washer.

I hope this helps!
 
Loose wire? We had two like this!

Breister:

Loose? You mean something like this? Not only did we crimp, we soldered too!

battleadfailure.jpg


Barry
 
MrNomad said:
Breister:

Loose? You mean something like this? Not only did we crimp, we soldered too!

battleadfailure.jpg


Barry
Click to expand...

Now please note that I'm not a master electrician. However, in my unscientific and unsupported opinion, I'll go out on a limb and agree with that...

:D

To those who went and bought the 2-wire GRT sensor (and I KNOW there are a bunch of you):

Congratulations, you may have successfully hidden a problem in your electrical system. Is that really the type of "solution" you want in your airplane?

:eek:

Fly safe, all.

Bill
 
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