J230 erratic oil temp readings

[flie43]

Ok guys, I have an oil temp problem I cannot solve as yet. We noticed the oil temps occasionally going haywire- from being nicely in the green to jumping up and down from 120-130 and down to 110 and back up and then sitting back on the normal level.

 

Yep, I know, it is a bad earth I think somewhere or maybe a faulty temp sender. We changed the sender on the block and all seemed good for about 10 hours and now back to fluctuating.

 

Did some testing in flight and found switching off or on strobes or beacon or nav lights and sometimes the PTT also brings it back to the normal readings for a little while.

 

Have tried obvious connections on sender unit etc, removed headsets but all too no avail.

 

Has anyone struck this problem and if so where did they find the fault ??

 

Any help greatly appreciated.

 

Terry

 

 

[brilin_air]

Terry,

 

Sounds like you are going on the right track with the guage, when you fitted the new sender do not use sealant if possible as it can insulate the sender and give bad readings also make sure the terminal connecting the sender wire is squeaky clean and tight on the terminal, then you can check the power and earth wires on the back of the guage to make sure of clean tight fittings, and failing all that maybe fit a diode on the back of the guage.

 

Good luck

 

Brian

 

 

[frank marriott]

Sounds like it could be the guage [in the dash].

 

"found switching off or on strobes or beacon or nav lights and sometimes the PTT also brings it back to the normal readings for a little while"

 

The guage will have an internal voltage regulator [usually about 10V] to compensate for varying supply volts - if this is faulty the readings will vary with supply voltage variations. The tests you have nominated are acutally varying the supply voltage momentarily.

 

Check if you get a variation between idle and 2000RPM - i.e. difference between battery voltage and charging voltage.

 

FrankM

 

 

[flie43]

Gee Brian and Frank,

 

I should have mentioned the instruments are Dynon EMS and EFIS.

 

Could your answer still be true with the Dynon gear or only for the Analogue guage ? We have retraced the sender wire and cleaned the connection, all seems clean and tight.

 

It's just bloody distracting and annoying and really got real worried when on a flight when it first happened thinking the big fan would stop before I could get down.

 

Thanks so much for your help so far and please keep coming back with suggestions if you have any as this area is not my strong point but I am learning heaps.

 

Terry

 

 

[Guest Andys@coffs]

Terry

 

In Which case I would rig an analogue guage to see what then transpires. Obviously if the issue continues its on the wiring/sensor side if it doesnt then its on the Dynon side. Wont take long and may well prevent you looking for issues where there are none....

 

That all said, a word of warning, the above test is not, unfortunately, definitive, there are occasions when an analogue guage that is by its very nature very slow moving will show nothing of transient errors, where a digital circuit such as that within the Dynon, that takes small snapshot in time as it does its sample and then displays the result until its time to take another sample can be affected by transients. If at the time of the sample there is a transient occuring then the display will show that transient voltage for a period likely much longer than it really occured for.

 

An electronics tech with a digital or older storage oscilloscope can possibly show what is really happening on the sender line if it gets to the point that you cant logically work out a way forward.

 

Andy

 

 

[frank marriott]

File43

 

"the instruments are Dynon EMS and EFIS"

 

Sorry mate I will buy out at this time as my comments are not helpful for your instruments

 

FrankM