oil pressure indication problem

[barry767]

Today we started my Highlander's Rotax 912 for the first time. The only problem was no indication of oil pressure on the Dynon 180. Actually it read 0 psi. Since the engine was manufactured after 2008, it is equipped with a Honeywell sending unit attached to the right forward side of the engine. We verified the wiring was correct and type 4 was selected on the Dynon's sensor page per the installation manual. The sending unit wiring involves 2 wires going to the Dynon display and one going to ground via a 180 omh resistor. Oil pressure was confirmed with a mechanical gauge and indicated 50 to 60 psi of pressure.

Has anyone else had this problem and if so, what did you do to get the Dynon to indicate properly? I suspect that the Honeywell sender is faulty but just want to make sure everything is installed and set correctly before sending it back to the manufacturer.

Thanks, Barry.

[User GDS]

When Rotax changed to the Honeywell oil pressure sensor unit, there were some problems with failure during the first 10 hours. The honeywell unit in my RV12 failed after about 8 hours. In the H, I have the Honeywell unit and have had no problems in 90 hours of flying. Did you put a volt meter on the leads coming out of the Honeywell?

The Honeywell unit is in the $300-$400 range. If you don't have warranty coverage, an option is to replace it with the old style, VDO unit, which costs about $50. The VDO is more prone to vibration failure and the voltage output is different. (either twice as much or half as much, I don't remember which) On the RV12, I installed the VDO unit and it worked well. At that price, you can buy a spare or two.

Another thing that people do is to install the oil pressure sensor on the firewall, where it doesn't get as much vibration. Lockwood sells a kit for <$200 if you want to do that. I'm more concerned about the vulnerability of additional pressurized oil lines than the occasional oil pressure sensor failure, so I haven't done that.

Here's a link with an in depth discussion of the subject on early RV12s: http://www.vansairforce.com/community/s ... hp?t=65042

[RV6]

Barry
I hope you did the oil purge system per rotex....

John

[barry767]

John,

We pressurized the oil tank to get oil through the engine and back to the oil tank prior to starting. I'm not familiar with the purge system. Can you elaborate? Barry

[barry767]

Found this post from 2006 on the internet:

On to the no oil psi indication during the process. I could find nothing wrong with wiring hookup so went into the Dynon. Pulled up the sensor page and it was correctly set to #4 type for a Rotax engine. At the suggestion of FAA guy watching (IA) I changed that to a #1 type, shut the Dynon off , re booted it and changed back to #4. The ensuing prop turning w/o top plugs in produced psi indications immediatly and quickly rose to about 65#.

Tomorrow I plan on giving this method a try and will report back on my success.

[barry767]

No luck...

Am going to give Dynon a call on Monday

[scubarider2]

Did you install an oil thermostat?
Dennis

[14PS]

My first post. SuperSTOL Serial 340 is on order. Tail number will be N14PS, Radio call sign will be Just14PapaSierra. I am Papa Sieren to my kids. Hope that isn't too cutesy for you folks, like some of those pukey personalized car license plates. Oh well, I was born in Iowa but used to live in California. Everything was cutesy there.

I do have a little contribution to the discussion in this post. Anybody who has a Honeywell pressure sender and also has a Dynon D180 EFIS, if you decide to replace the Honeywell with the much less expensive VDS unit (available from Lockhart), you will need to remove the 200 ohm resistor that is shown in the Dynon manual. Otherwise, the oil pressure will read way low on the Dynon. On my RV12, that resistor was buried in a stack of PC boards behind the circuit breaker panel, so I just cut the pressure sender lead and ran it directly to the Dynon. This solved the problem, and the Dynon now reads the same oil pressure as a temporarily installed mechanical oil pressure gauge.

Hope this information is useful to somebody.

JSieren, New Harmony, Utah

[barry767]

Thanks, JSieren. If I have to remove the Honeywell unit and replace it with something else your post will be very helpful.

Dennis, yes I connected the wire for oil temp and it appears to be working correctly on the Dynon.

[accent air]

I don't know if you had luck with Dynon today but if not Email or call me I think I know what the problem is with oil pressure

[scubarider2]

Just a thought on the oil thermostat. If not connected correctly it will show no oil pressure but temp will show. Just worth a check. I know from experience
Dennis

[barry767]

Dennis,

You called it. I actually had two problems. One, I connected the wrong red wire. There are two red wires on the 37 pin Dynon harness: #1 and #15. I connected #1 instead of #15 to the red wire of the sender. Second, I installed a 220 omh resistor to ground instead of a 200 omh resistor which is what the installation manual calls for. Once both of these were corrected, I started the engine and I was reading 65 psi of oil pressure at idle and 0 psi when the engine was off!

Barry