High oil temp issue Hdx Continental Io 550 N

[LouRubin]

I converted my panel from GRT to Dynon and for the most part I’ve been very happy.
I did notice my oil temps went up alot after the conversion and thought I might have a bad vernatherm
valve,probe,or oil cooler . My CHTs run very cool 300F or less. I replaced these items and the issue remains. After many hours of trouble shooting there is a correlation between turning on the avionics switch and alternator with rising temps on the gauge.When I shut down the temps drop 15 degrees or more.I presume i have a grounding problem somewhere thats causing the issue.The gauge reads perfect checked with a laser gun at the ambient temp engine off.It appears the error compounds the hotter the temps get. I’ve seen over 245 degrees in flight which starts fluctuating to 260 or more. My pucker factor goes thru the roof.
The old GRT probe had a ground terminal which probably helped keep it accurate. My question is
where should I look for a ground issue? Would it make sense to solder a ground wire to the oil temp probe.Everything else works fine but I did notice the oil pressure drops inversely with temps rising.
What makes this scary is I don’t know if the oil temp is lying or not The oil pressure drops around 15 psi however I’m not sure if it’s also affected by a ground issue or the high temps are actually lowering the oil pressure. My Chts and and Egts seem normal and stable.

 

[jakej]

The best grounding method is to connect the sensor ground to 1 of the EMS module grounds - if you run out of grounds there then just join into 1 of them.
you are using the Dynon (Kavlico) pressure sensors, correct?

 

[LouRubin]

I’m using a Kavlico sender for fuel pressure The oil temp sender is what’s sold by Dynon. There is no ground terminal . I believe the oil pressure is a VDO sender which I’m in process of switching to Kavlico. Are you saying connect all the sensor grounds to number one?

 

[LouRubin]

I checked the oil temp sensor ground and it’s showing perfect ground continuity with no resistance at all. I wonder if the issue could be a poor ground on the EMS?

 

[jakej]

I’m using a Kavlico sender for fuel pressure The oil temp sender is what’s sold by Dynon. There is no ground terminal . I believe the oil pressure is a VDO sender which I’m in process of switching to Kavlico. Are you saying connect all the sensor grounds to number one?

A bit of clarity here. - the pressure sensor grounds, fuel flow, map sensor etc should be connected to the ground wires ( there are several of them) that are available out of the EMS module - the Oil Temp sensor body uses the engine case as a ground, there is no separate ground wire for it. all the grounds are paralleled inside the ems module.

 

[jakej]

I checked the oil temp sensor ground and it’s showing perfect ground continuity with no resistance at all. I wonder if the issue could be a poor ground on the EMS?

If you have 1 x Ems ground wire going to a good airframe ground then that will work.

 

[LouRubin]

Thanks Jake
I presume there’s an option to piggy back the grounds to pin 17 as depicted by the schematic or use multiple grounds from the EMS?I’m confused why the oil temp probe doesn’t pick up the ground from the EMS since the idea is to keep the electrical potential as close as possible.I’ll be confirming all the pressure sender grounds terminate at the EMS I hope this solves the issue

 

[jakej]

Thanks Jake
I presume there’s an option to piggy back the grounds to pin 17 as depicted by the schematic or use multiple grounds from the EMS?I’m confused why the oil temp probe doesn’t pick up the ground from the EMS since the idea is to keep the electrical potential as close as possible.I’ll be confirming all the pressure sender grounds terminate at the EMS I hope this solves the issue

To make things easier I join the pressure sensors grounds onto the MAP sensor ground - has worked for Hundreds of hrs. The standard Dynon Oil Temp sensor does not have a ground wire however if the temp sensor you have (hopefully compatible) has provision for a ground then ground it to the Dynon EMS grounds.

FYI, & for others watching - you don’t need to go back to the EMS module, just join onto one of the grounds coming out of its wiring loom - double up if you need more grounds than are available.