J

JohnF

Well Known Member
Just sitting overnight in the hangar my D-180 OAT decided it was -46F. I have looked at MANY pages of Dynon forums and unless I miss my guess I have a bad proble. I will call Dynon tomorrow and I know they will want resistence readings...and if the probe is bad, as I suspect is it, I want you to imagine trying to remove the probe itself and all the bundled wires that go back to the compass. I would have to drain the fuel tank, remove it, tear up the main "tunnel" cable to 'fish' out the probe wires, remove the seat/seat backs, and crawl back into the tail....

I am really beginning to think I would prefer steam gauges...this is getting out of hand.
 
John, before you go to all that work find out which pin the OAT goes to and test it behind the panel. My guess is something is wired wrong.

Did you do the test on the CHT probe?
 
OAT

No, it can't be wired incorrectly because it was working properly. When I turned off the power at the D-180 all was fine. Next morning it locked itself to -46F and nothing was done in the meantime..no engine run, no aircraft movement. I know it was working OK because the last thing I did was to compare the OAT, my EGT, and CHT when everything was cold, remembering the CHT problem I had just resolved. All three of these readings were within a few degrees, so OAT was just fine. Unless the lead length is a factor, if I have to replace the OAT probe I would cut off the old one and use the leads that go to the compass that are already there...we'll see what Dynon says, but their forum is full of complaints of bad OAT sensors.
 
Funny coincedence

In that I think something is up with my probe into the edc-10a too. I've yet to do a pin check. Symptom is simple, in the past three weeks (since I lit up the panel) it's been 22c. Always. We shall see. Rick 90432
 
OAT resistance readings

John,
I took resistance readings of my temp probe before installing it. Here they are if they are any help:
OAT-2 YEL Remote Compass D-SUB-9 Pin 2
OAT-7 RED Remote Compass D-SUB-9 Pin 7
OAT-8 BLU Remote Compass D-SUB-9 Pin 8
Pin 2-7 = 9.96K Ohm, Does not change with Temp
Pin 7-8 = 23.5K Ohm @ 65 Deg (Varies with Temp)
Pin 2-8 = 13.7K Ohm @ 65 Deg (Varies with Temp)
It is possible the probe is bad. But more likely is a bad connection. And Murphy's law says that the problem is most likely at the D-Sub connector in the tail cone.
If you do have to remove that access panel to the tail cone, then while you have it out, engineer fasteners that do not require removal of the fuel tank. I was thinking that a pin fastened on the access panel could be inserted into a hole drilled into the bulkhead frame. It should not be necessary to remove the fuel tank to get at troublesome wires in the tail.
Joe
 
OAT

Rick, try looking at the Dynon forum pages...I saw quite a few problems regarding the 10 and the OAT, in fact I recall one talking about the 22-degree problem you have...don't recall their answer, but their forum pages might help you. If I can resolve my problem I will post the info one what was done'/changed
 
OAT

Joe, I fully agree: It should not be necessary to remove the fuel tank to get at wires in the tail. But you cannot remove the aft baggage wall closure without removing the fuel tank because there are a few screws that are covered by the tank.
JohnF
 
OAT

Well, Dynon says it looks like a bad probe, but you can't be certain unles you go to the plug and make the resistance measurements.

All I have to do is to remove the cushions, seat backs, remove inspection plate, drain the fuel, remove the fuel tank, remove the baggage wall closure, lay planks back into the tail cone and try to make measurements laying on my back.

Quite simply, this isn't worth the work...I would forget about OAT and set it manually, which the D180 installation books says can be done, but it doesn't tell you how to do it. The Dynon technical help didn't seem interested in telling me how to do it either...main point was to get me to shutup and hang up the phone.

The wiring for the probe is so 'buried that its removal would be a damaging operation.

Right now I am ready to sell this thing and do something else !!!
 
OAT

Does anyone know how you can set the OAT GP #3 input to "N," or no OAT probe, and then set the OAT manually? ( I know how to set it to "N")

The installation manual says you can set OAT manually, although it doesn't tell you how to do it, but as I noted in a post a bit ago, DYNON tech was not interested in telling me how to do it. My thinking now is to set it manually, get on with wrapping up the plane and get the airworthiness cert and worry about the probe later.

As long as I can set the OAT it shouldn't matter in regard to airworthiness how it is set, as long as it is...Mel, do you agree?
 
From page 5-14 in the D-180 pilot's user Guide:

OATSET ? Setting Temperature Offset
If you did not purchase an EFIS or EMS outside air temperature sensor from Dynon Avionics, you may still manually adjust the OAT to an approximate value. With this manually entered information, the FlightDEK-D180 calculates and displays true airspeed (TAS) and density altitude as it does when an OAT is connected. Ensure that you have indicated that an EFIS OAT is not installed; enter the EFIS > SETUP > OAT menu and press INSTALLED until the value is ?N.?
EFIS Operation
In the EFIS > OATSET menu, press INC- or DEC+ until the value-setting box above the menu displays the current outside air temperature. This value is then used in the OAT/TAS/DA info item on the EFIS screen. For more information on setting up that display, see page 5-12.

I haven't gotten this far so not certain it is what you are looking for.

I can imagine the frustration of having to dig your way to the back of the plane to troubleshoot this, but I think it is worth doing. You've gone this far - only a little ways to go;)
 
Aft Baggage Wall

JohnF said:
Joe, I fully agree: It should not be necessary to remove the fuel tank to get at wires in the tail. But you cannot remove the aft baggage wall closure without removing the fuel tank because there are a few screws that are covered by the tank.
JohnF
Click to expand...

John,

Before you cut up the aft baggage wall you may want to talk with Vans. That is very possibly a structural issue.
 
OAT Problem Resolved

Two folks from Dynon didn't get it right, but after doing everything I could think of short of tearing up the plane to get at the end of the OAT wiring at the magnetometer, I began to think of the times I turned on my home laptop or desktop and they didn't "come up" correctly because something was corrupted during the start up process. I wondered if the D180 might sometime suffer the same transient fault. So I looked at everything I could find and made as sure as I could that things were set correctly. I undid the things I could, and reset them and lo and hehold! It began to work correctly.

I think there are 6 or 7 inspection plates on the bottom of the plane. There should be another one on top of the fuselage just forward of the magnetometer so that if you need to get to the plug from the OAT that it can be done that way instead of tearing up the airplane.
 
Good going John

Let's hope that the problem was solved by "rebooting" and that it is not an intermittent problem that just happened to go away. If the problem does occur again, it could be in one of those connections that you touched.
I know that you must be relieved not to have to remove the fuel tank and crawl into the tail.
Joe
 
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