Oil Temp reading low

I am not sure this is a normal failure mode but my oil temp in the middle of a flight went from reading 190 to 145 and then stayed there.

I found the nut holding the sender wire ring terminal loose. I tightened it up thinking problem solved. Well next flight oil temperature still reading abnormally low basically 50 degrees lower than what is actual.

At this point I am guessing an new sender is in order, it has never given me any issues.

Has anyone seen this failure mode before, what did you find was the problem. I also have a CHT that has started to act funny, checked that it was seated in the mount but at this point it is very intermittent.

Thanks for any suggestions.

I had the same thing. New sender should fix it.

Id bet money its the sender

It could of course be a bad sender, but 2 different senders acting up at the same time may be a clue that something else,that is common to both, is the culprit. Grounds between the engine and airframe, sender and the indicator come to mind. Checking and cleaning these takes a small amount of time and requires no money.

Possible the Temperature control, oil cooler bypass valve is stuck open. Oil will then be sent through the oil cooler instead of being bypassed back to the oil sump until the oil warms up. Just a thought.

Test the sender

Test the sender first by putting it in a cup of boiling water - you should get 212 F or close to that. Remember to ground it while in the cup. I had two of them do the same on two different aircraft.

As mentioned above if more than one sensor act funny at the same time it is worthwhile to clean and retighten your ground connections.

Question

chevytoo said:

Possible the Temperature control, oil cooler bypass valve is stuck open. Oil will then be sent through the oil cooler instead of being bypassed back to the oil sump until the oil warms up. Just a thought.

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This happened in the middle of a flight, it went from reading normal to instantly reading low by 50 degrees. I found the nut holding wire on the end of the sender loose and tightened and thought I had it solved but next flight it still read low.

New sender arrived so I will give that a try and check for loose grounds

Cheers