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Oil temperature and CHT jumping around

j4cbo

Member
The other day I was flying around and noticed my oil temperature jumping into the yellow. It was spiking up and down by about 30 degrees every second or so - much faster than the temperature could actually have been changing. I took a video, and noticed that the CHTs (but no other sensors) were doing the same thing.

On looking at the schematics, I noticed that oil temperature and CHT are the only sensors that are grounded via the engine case rather than having dedicated return lines. I also don't know how the EMS-220 is grounded... looking at the PDF and AutoCAD files seems to show that none of the EMS-220 GND pins are connected? So I don't know what the ground path for those sensors is supposed to be - via the starter motor to the airframe, and then through SV-NET to the EMS-220, I guess?

Anyone seen anything like this before?
 
On the -12iS, and likely the -12, there is a short wire near the starter which grounds the engine to the airframe. Perhaps that wire is loose or has some corrosion?
 

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Adding additional grounds may not solve all of the flaky sensor problems but can not hurt! Consider adding an additional engine ground to unused metric threaded hole on left side of engine case. The iS firewall probably does not have a nut plate location as shown here on my early build, but this is an example of how additional grounding could be done (after certification, naturally).
 

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I had the same problem. I found the temperature sensor that is an electrical slide connector attached to the front of the engine near the oil pump housing. I pinched it with a pair of pliers so that it would make a better connection it took care of the problem. Every once in a while I have to pinch it again. I don't think that is a very good design for an electrical connection as it slips onto a post that can swivel.
 
Whoops, looks like my attempt to attach a video clip didn't go through. Here's another try. See how correlated they are...

I just got back from a week out of town so I haven't been back to the plane yet. Tomorrow I'll double check all the grounds I can find.
 

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Hey There- not a RV-12, but I had the same issue on my oil temp on my 7 with a 390 (similar jumps in temp not physically possible). Cleaned up my ground on the engine case has some paint overs spray from the factory) and she's been rock solid since.

Seems if you are seeing similar issues on two set of sensors the ground would be a good place to start.

best of luck
 
Also no idea how you are getting that manifold pressure above 30 inches? Somewhere, a ground wire is in need of some attention, all your gauges are jumpy in values.
 
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