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Oil Temperature fluctuations

n518jh

Member
Recently my Rotax 912 ULS and Dynon 180 Oil Temperature system has gone wild at altitude. Doesn't seem to happen on startup and warmup or for the first few minutes. Then the needle jumps all over going down to 100 degrees and the scale goes to warmup, etc. Then comes back for a while, etc.

I checked the connection to the temp sensor and it seems OK, and haven't traced it back to the Dynon, hoping someone has had the same problem and can show the way. I am not the builder, so I have second owner problems of wondering what the builder did on my RV-12 EAB. Help Mark
 
Most likely a bad ground to the sensor or a failed sensor. If it is directly attached to the engine they tend to fail prematurely due to the pulses from the oil pump and the engine vibrations.

Vic
 
Count yourself lucky. Recently all my CHT, Oil Temp and EGTs started spiking randomly. Dynon has my D180 for evaluation. I?ll post when they get back to me.
 
Oil Temp Fluctuations

I called Aircraft Spruce and talked to a Rotax expert. He suggested replacing the sensor as the easiest and cheapest (in time). I have the replacement and am waiting to get to the hanger to try it. Including shipping $18. Mark
 
Mark,

I hope it works for you. Dynon is checking my D180 now. Seems strange that my oil temp, EGT temps and CHT temps ALL went squirrelly at once, but not in synchronized swings. I hope they find something wrong to fix.It could be a connector I guess, but I would have expected the 5 to spike in synch.

Rich
 
Your first trouble-shooting action should be to check all grounds including the primary engine-to-airframe ground -- especially if multiple gauges are involved. Even if the grounds externally look and feel satisfactory, it often helps to disassemble and thoroughly clean the connections.
 
Cleaning the ground wires is something easily over looked, I thought I had a bad starter once, turned out to be not a loose ground but a bad ground, had a little corrosion but that's all it needed to cause the starter not to turn, everything else was powered...check and clean the grounds.
 
Improving grounding

The RV-12 engine to airframe ground is one heavy white wire on the right hand side of the engine. I decided to add a similar ground wire on the left side and attached it to a vacant cylinder head screw hole direct to the AN4 screw that is used for the regulator mount on the firewall shelf. My regulator has moved to the inside location so I ran another ground directly to it's new location. There is also a another ground wire from the AN4 regulator screw over to the negative battery terminal. You can't have too many grounds ;)
The cylinder head screw hole is threaded 6mm metric and a proper plated 6mm hex head screw is hard to find in local box store. The best choice is a Rotax screw part number shown on the picture.
i-HCB4tdw-L.jpg


Also consider taking preventive measures against corrosion of connections:
i-tbrgw6C-L.jpg

There are three slip-on sensor connections that can easily lose good contact:
The two CHT sensors and also the connection to the oil temperature sensor on the front of the engine which, in this case, could be a possible cause of the OP's intermittent problem.
Just some ideas that can't hurt and may help these kind of issues.
 
I posted about spiking of my Oil, EGT and CHT indications about 5 weeks ago. Cleaning the connector contacts didn?t solve the problem, so I sent my D180 back to Dynon for troubleshooting. They ended up replacing the EMS board. An initial short flight showed normal temperature indications, so hopefully the issue is fixed. Don?t rule out a D180 issue.
 
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