I have an EMS 120 in my lycomming IO 360 M1B powered RV 7. I have had an oiltemp indication that continually fluctuates. at the bottom of the green the fluctuation is over a range of 3 degrees. As the temperature rises the extent of fluctuation increases. By the top of the green it is 6 degrees fluctuation. Makes it quite difficult. I have replaced the probe with a new one from Dynon and installed the latest firmware to no avail. All the other indications are rock solid including the manifold pressure which I fixed with a little foam in the line. Can anyone out there or from Dynon give me any help? It is a really frustrating problem particularly in hot weather! Ric Macready
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fluctuating oil temperature indication
- Thread starter acedunno
- Start date
- Joined
- Mar 23, 2005
- Messages
- 13,226
This is basically always a ground problem between the engine and the airframe or battery.
The oil temp sensor is very sensitive to voltage offsets, and gets more sensitive at higher temperatures. Since it shares a ground with the engine case, any poor ground the engine has, the oil temp sensor has.
You can prove this by turning off the alternator when the engine is running. This removes all of the current from the ground path, and your oil temp will suddenly be stable.
You cannot just run a ground from the EMS to the engine. It's hard to describe, but unless you made this wire a zero gauge wire, it won't help, since it ends up in parallel with your other bad ground.
Many people say they have a good ground, but when they look at it, they have the ground wire hooked to a painted part of the engine, the ground strap is corroded, the battery cable is loose, or something else.
Spend some time investigating the ground between the engine, airframe, and battery and you'll find something amiss. On the plus side, this is warning you that al your electronics have an iffy ground, so this should make the whole electrical system in your plane more reliable.
The oil temp sensor is very sensitive to voltage offsets, and gets more sensitive at higher temperatures. Since it shares a ground with the engine case, any poor ground the engine has, the oil temp sensor has.
You can prove this by turning off the alternator when the engine is running. This removes all of the current from the ground path, and your oil temp will suddenly be stable.
You cannot just run a ground from the EMS to the engine. It's hard to describe, but unless you made this wire a zero gauge wire, it won't help, since it ends up in parallel with your other bad ground.
Many people say they have a good ground, but when they look at it, they have the ground wire hooked to a painted part of the engine, the ground strap is corroded, the battery cable is loose, or something else.
Spend some time investigating the ground between the engine, airframe, and battery and you'll find something amiss. On the plus side, this is warning you that al your electronics have an iffy ground, so this should make the whole electrical system in your plane more reliable.
greatslave
New Member
- Joined
- Mar 29, 2009
- Messages
- 1
I had a similar problem when I first had my EMS installed. The mechanic figured it was a ground problem so he removed the probe, cleaned all of the contacts, and re-installed it, and it has worked perfectly since.