RV-12 Need help with AV board

[richardsmi]

I have a new un-flown RV12 in the UK.
The Dynon is giving Zero oil pressure even though we know the Rotax has actually got oil pressure.
The Honeywell sensor has failed and I think that it has caused a problem in the VA/ fuse/ panel to the left of the cockpit.
Checking the red wire which feeds the oil pressure sensor there should be a 12volt supply.
All the earth/ground connections are zero resistance to each other ie battery terminal, Dynon case and engine block.
ther is a 12volt supply out of the Dynon and into the AV
Has any one got a circuit diagram for the AV unit.
Or better still has anyone had a similar experience and overcome it?
I want to get flying!

 

[Gagarin737]

PM me your mail-adres for a zip file.

 

[Mich48041]

Oil Pressure sender circuit

I connected the negative terminal of a flashlight battery to ground and the positive terminal to the Dynon D-180 EMS pin 6, which is for the oil pressure. The numbers below are from actual experiments.
3.19 volts = 29psi
3.28 volts = 37psi
3.33 volts = 41psi
3.80 volts = 84psi
It looks like for every 1/10 of a volt change, the oil pressure changes by 9psi. The Dynon probably expects to see between 3 and 4 volts on pin 6 that will correspond to zero to 100 psi.

I think that it has caused a problem in the VA/ fuse/ panel to the left of the cockpit.

The RV-12 control board has only one component related to the oil pressure sender, and that is a 200 ohm resistor. Disconnect the FIREWALL FORWARD and EFIS D-Sub connectors from the control board to isolate that resistor. Using ground as a reference point, measure the resistance on the back of the control board (NOT the cables) at the following points: Pin 15 of the firewall D-Sub and Pin 22 of the EFIS D-Sub. Each of those pins on the back of the control board should measure 200 ohms to ground. If they do, there is nothing wrong with the control board that would cause an oil pressure error.
PM me for more info.
Joe Gores

 

[richardsmi]

Av board and oil pressure

Firstly my thanks to both Joe Gores and Gargarin 737 for a speedy and helpful reply which lead me straight to a solution.
Recapping I had just bought my RV12, already built.
There had been oil pressure showing on the Dynon but then there wasn't. We were pretty sure that the Rotax had oil pressure, they are very reliable and eventually found by using an analogue oil pressure gauge that the reading across the Honeywell oil pressure sensor was full gauge/ max pressure when the engine wasn't even turning. This told us the sensor was shot, BUT, and this is where I complicated it for myself, I looked for a 12volt supply on the red wire feeding the sensor and there was no supply.
My immediate thought was that, in failing, the sensor had created a secondary problem, perhaps on the AV board (resistor blowing?), hence my first ever request to the VAF forum re the AV board.
The problem I really had was that in all my training I had been taught not to fire up the avionics kit until after the engine had been started ( whether this is necessary or not isn't the point) my training was stopping me from switching on any of the other switches when checking for a 12 volt supply to the oil sensor.
When I had been advised to switch on Hey Presto 12 volts duly appeared!
Thanks guys for your support.

 

[Geico266]

Welcome to VAF Richard!



Thank you for posting the success you had due to the advise you got here. There is a ton of great info on the -12 here. Hope it helps you in transition. Don't be a stranger!