bmarvel
Member
Hi all:
Off and on for the past year we have had erratic oil temperature indications on our EMS D-10. The aircraft (Zenith 801) is powered by an O-360 with an oil filter installed. Sometimes oil temp was stable and sometimes it bounced from 45 to 350 degrees F in a matter of seconds. Alerts were going off all the time. Tracking down all wires and even changing the oil temperature sensor did not reveal the cause of the problem.
Dynon said this is normally a ground problem and to check the ground between the engine and airframe. It is a number 4 welding cable installed to an engine oil sump bolt at one end and on a B&C ground block mounted on the firewall at the other end. I installed it myself and made sure there was good metal to metal contact on both ends. I had to sand off some paint on the engine to make sure the connection was good. Everything worked perfectly except for the oil temperature gauge so I was confident the ground side was OK. Well, it was -- except for one subtle little item that I discovered a few days ago.
The oil temp sensor is screwed into the oil filter adapter, which then grounds to the accessory case and then to the engine and eventually to the airframe via that number 4 welding cable. BUT, the oil filter adapter is separated from the engine accessory case by a gasket that does not conduct electricity. The ground has to be made through one or more of the four bolts that hold the adapter to the accessory case. Our engine was built up new and all parts were painted. What I wondered -- correctly as it turned out -- was if no one ever thought to scrape the paint off the bearing surface of the adapter where a bolt head and washer rested against it. So I pulled out the easy to reach upper right bolt and bingo -- a thick coat of Lycoming gray paint was still nicely in place. I assumed all four were just like this so I scraped off the paint, cleaned the contact surface and reinstalled that one bolt. Everything has been accurate since. We had a very poor and intermittent ground because of this seemingly small detail.
Summary: Just because your engine case is properly grounded to the airframe does not mean that every component mounted to the engine is properly grounded to the engine itself. This is worth remembering!
Bill Marvel
Zenith 801 and RV-8A
Grand Junction, Colorado
Off and on for the past year we have had erratic oil temperature indications on our EMS D-10. The aircraft (Zenith 801) is powered by an O-360 with an oil filter installed. Sometimes oil temp was stable and sometimes it bounced from 45 to 350 degrees F in a matter of seconds. Alerts were going off all the time. Tracking down all wires and even changing the oil temperature sensor did not reveal the cause of the problem.
Dynon said this is normally a ground problem and to check the ground between the engine and airframe. It is a number 4 welding cable installed to an engine oil sump bolt at one end and on a B&C ground block mounted on the firewall at the other end. I installed it myself and made sure there was good metal to metal contact on both ends. I had to sand off some paint on the engine to make sure the connection was good. Everything worked perfectly except for the oil temperature gauge so I was confident the ground side was OK. Well, it was -- except for one subtle little item that I discovered a few days ago.
The oil temp sensor is screwed into the oil filter adapter, which then grounds to the accessory case and then to the engine and eventually to the airframe via that number 4 welding cable. BUT, the oil filter adapter is separated from the engine accessory case by a gasket that does not conduct electricity. The ground has to be made through one or more of the four bolts that hold the adapter to the accessory case. Our engine was built up new and all parts were painted. What I wondered -- correctly as it turned out -- was if no one ever thought to scrape the paint off the bearing surface of the adapter where a bolt head and washer rested against it. So I pulled out the easy to reach upper right bolt and bingo -- a thick coat of Lycoming gray paint was still nicely in place. I assumed all four were just like this so I scraped off the paint, cleaned the contact surface and reinstalled that one bolt. Everything has been accurate since. We had a very poor and intermittent ground because of this seemingly small detail.
Summary: Just because your engine case is properly grounded to the airframe does not mean that every component mounted to the engine is properly grounded to the engine itself. This is worth remembering!
Bill Marvel
Zenith 801 and RV-8A
Grand Junction, Colorado