Sport Pilot Talk

Hey,

Today I noticed one side CHT reading became erratic during flight . It was jumping now and then about 20-40 degrees back and forth pretty much instantaneously.

Here is a short clip of that happening :
https://www.youtube.com/watch?v=Lctv5uH ... e=youtu.be

I assume this is just a sensor ( it is about 8 years old or so and the engine ran just fine ) so the question is what would be the next course of action ?

Clean the spade connector ( I have the older design , placed under the cylinder ) ?
Check the engine ground ?

If I were to clean the connector , should I just clean it/scrub it or is there some recommended conductive lubricant I should use ?

Thanks

When sensors fail, they generally fail dead. Erratic readings are almost always intermittent wiring problems. By all means clean your spade connectors (I usually use Scotchbrite, and smear on a thin film of silicon grease afterward). The ground connection is often the first to go. Good luck - you can solve this!

There are two types of CHT sensors, Thermistor and Thermocouples. The thermistor is a temperature sensitive resistor that changes resistance with temperature. In a Dynon EMS system it is wired in series with a small resistor and the junction point is read by the EMS, these are prone to problems. The second type, the thermocouple is a bimetal sensor that generates a small voltage with respect to temperature that is read by the EMS, they are almost foolproof. The D120 has direct inputs for EGT and CHT thermocouples and are rock steady.
I had problems with my D120 using the thermistor and found the issue to be a bad ground for the system. Eventually I changed to thermocouples and was happy ever since.


Good luck with your repair

Randall Bearden
Sport Pilot
LSRM-A

I have cleaned , greased and re-seated the relevant spade connector and haven’t had a single erratic reading in a week - so far so good.

Thanks

RBearden56 wrote:There are two types of CHT sensors, Thermistor and Thermocouples. The thermistor is a temperature sensitive resistor that changes resistance with temperature. In a Dynon EMS system it is wired in series with a small resistor and the junction point is read by the EMS, these are prone to problems. The second type, the thermocouple is a bimetal sensor that generates a small voltage with respect to temperature that is read by the EMS, they are almost foolproof. The D120 has direct inputs for EGT and CHT thermocouples and are rock steady.
I had problems with my D120 using the thermistor and found the issue to be a bad ground for the system. Eventually I changed to thermocouples and was happy ever since.


Good luck with your repair

Randall Bearden
Sport Pilot
LSRM-A

Which kind does Rotax use?

On my 912 ULS I’ve replaced the left side CHT sensor twice in 585 hours.
It would jump from normal to high then low triggering the yellow/red warnings.
Crimping/lubing the spade connector helped a bit.
In the end just bought a new sensor, life’s too short!

fatsportpilot wrote:Which kind does Rotax use?

Rotax uses a VDO temp sender. It's the same part for the CHT and oil temp. VDO part number is stamped on the sender. 801/10/1. These are the senders in my 2007 Rotax engine.