Erratic CHT and/or EGT ?

My Dynon EFIS has had occasional erratic readings, including the RED X, almost from the start (200+ Hobbs). My wiring connections were rock solid. The grounds were all to the forest of tabs. The sensors were all new. I had Dynon verify my EMS box was operating correctly. So This week i finally decided to dig into the wiring. A post on the Dynon forum recommended special Thermal Wire connectors from Omega. $3.50 each. Ordered them and installed them.
Today did a 4 hour round trip to Myrtle Beach KMYR. All engine readings STABLE!! And movement appeared totally logical with adjustments of throttle, mixture & prop controls. Only 4 hours, but it appears my ?rock solid? KNIFE SPLICES between the wires from the EMS box and the engine sensors weren?t as solid as they needed to be. The Omega Thermal Connectors seem to have solved my problem.
In case others are having similar issues, try these connectors. They are the SMPW type. CHTs are Black/ J type. EGTs are Yellow/ K type.

I?ve had the same issue a few times and have just replaced the sensors. Do you have a link to the particular connectors you used?

Www.Omega.com
Search SMPW
Thermocouple Connectors
These are the part numbers:
SMPW-CC-K-M Yellow EGT
SMPW-CC-K-F Yellow EGT
SMPW-CC-J-M Black CHT
SMPW-CC-J-F Black CHT
U will need 4 of each. M for male and F for female.
They have a nice diagram of the install also.

Those are all two prong plugs. The egt/cht wires are single wires, right? Are you only using one of the actual plugs?

Latech15 said:

Those are all two prong plugs. The egt/cht wires are single wires, right? Are you only using one of the actual plugs?

Click to expand...

I'll answer for him...no, they're two-wire.

I have one of those connectors and am waiting for another EGT connection to act up (one inevitably does) to replace it and give it a try before going whole-hog and replacing all the EGT and CHT connections. It does look like a nice connector, though.

A dumb question

So here's a really dumb question: are these connectors used to splice the brown wires that run from the EMS to the CHT's and EGT's....or are they used to make the connection from the brown wires to the probes themselves?...I'm sure the later. That junction a very difficult connection to make. That connection can't be soldered due to the exotic material that those probe wires are made from (I think maybe Inconel) and you really can't crimp that either. I've personally struggled with this connection and have seen erratic temperature readings along with dreaded red X. If these connectors make the connection between the brown wires and the probes and fix the connection/continuity issues, this would be a real blessing.

Mark

Buy a handful of OLC-1's from Aircraft Spruce. Install ALL the connections between EGT and CHT probes to harness wires with these.

Do not waste your time and money doing anything else.

I have solved dozens of aircraft problems with these, not just Dynon either. Garmin, JPI........

I buy them by the 100 or more.

Problem solved

The brown wires from the EMS box have 2 wires within them. A white and red for one and yellow and red for the other. They appear to be made of differing materials, as mentioned above. The Omega Thermal connectors are 2 pronged and have a positive and negative identifier and also appear to be made of differing materials. I connected the white and yellow as negative considering that red is never ground. I cut the provided spade connectors off the sensor wires and replaced with the Omega?s.
Obviously more than one way to skin the cat. U can now choose. Something about connectors designed for Thermal purposes that make me like this solution.

pilotkms said:

The brown wires from the EMS box have 2 wires within them. A white and red for one and yellow and red for the other. They appear to be made of differing materials, as mentioned above. The Omega Thermal connectors are 2 pronged and have a positive and negative identifier and also appear to be made of differing materials. I connected the white and yellow as negative considering that red is never ground. I cut the provided spade connectors off the sensor wires and replaced with the Omega?s.
Obviously more than one way to skin the cat. U can now choose. Something about connectors designed for Thermal purposes that make me like this solution.

Click to expand...

On types J,K, N thermocouple wires red is actually ground.
http://thesensorconnection.com/cont...type-k-j-and-n-usa-and-international-iec-5843

Ok. Red to ground. I?ll change them. Easy with these connectors. Will see if they work as well.

Thermocouples

There is no ground. Polarity is critical though. Each wire is a different alloy and the connecting wires must match to each other and both connect back to the instrument/EMS. Each point where dissimilar metals touch, an additional millivolts potential is generated that will affect accuracy.

Re: polarity:
Confirmed it in the Dynon install manual in the EMS area. Positive is Yellow for K wire and white for J wire. Therefore the red wire is negative. I will reverse mine shortly.

Thanx for the correction.