CHT #3 error reading

[henriquerv7]

Good evening,

I have a dynon d120 for 5 years right now. Yesterday when i started my engine i noticed a huge variation in CHT#3 reading while taxing (from -55 to 250) After take off, the temperature start climbing and reading +999 including in cruise flight and descend. The others CHT and EGT temperatures was ok and steady. I started thinking the problem was in the probe, so today i switched the probes from Cyl #1 and #3 to eliminate the a defective sensor. For my surprise, just after the engine start the CHT #3 was showing +999 while engine still cold. I had help from a lycoming meachnich and he checked the engine, it was running smooth without any indication of problem in cylinder #3. Do you guys have any idea wheres the problem could be? Can be a internal dynon problem?

Regards

Henrique Castro

 

[dynonsupport]

Henrique:

Good troubleshooting to swap the sensor and having the problem remain at CHT #3!

Problems like this are very rarely internal to the D120 (or other EMS units).

Now that you know it's not the sensor itself, the next most likely thing is the connectors / junctions between the CHT/EGT harness and the sensors. That is often a problem with erratic CHT/EGT readings. Cut off the connectors on the harness of CHT #3 and install new connectors. Make sure the wire makes GOOD, solid contact with the connector.

If that doesn't fix it, disconnect the 25-pin connector and make sure all the pins in the connector are fully seated into the connector. An easy test is to hold the connector in your hand and with a pair of needle nose pliers, gently push in on the pins to see if they move. If the pin moves, even slightly, that pin is loose and could be causing the problem That pin needs to be firmly seated in the connector - sometimes (in extreme cases where the socket of the connector won't seat the pin correctly) it's necessary to de-pin the connector and re-install a new connector. In the case of CHT #3, the pins to really focus on are:
Pin 20 (White wire)
Pin 8 (Red wire).

Good evening,

I have a dynon d120 for 5 years right now. Yesterday when i started my engine i noticed a huge variation in CHT#3 reading while taxing (from -55 to 250) After take off, the temperature start climbing and reading +999 including in cruise flight and descend. The others CHT and EGT temperatures was ok and steady. I started thinking the problem was in the probe, so today i switched the probes from Cyl #1 and #3 to eliminate the a defective sensor. For my surprise, just after the engine start the CHT #3 was showing +999 while engine still cold. I had help from a lycoming meachnich and he checked the engine, it was running smooth without any indication of problem in cylinder #3. Do you guys have any idea wheres the problem could be? Can be a internal dynon problem?

Regards

Henrique Castro

 

[henriquerv7]

Dear Dynon,

Thanks a lot for the prompty reply, i will try it, i will let you know how my test goes!!

henrique