Rotax 912 Oil Pressure Sensor Problem

Technical questions, advice, sharing information etc (aircraft, engines, instruments, weather and such)
Dobbs
Survived second engine out
Survived second engine out
Posts: 358
Joined: Tue Jun 07, 2005 8:10 pm

Re: Rotax 912 Oil Pressure Sensor Problem

Postby Dobbs » Sat Mar 08, 2014 6:55 pm

After 2 failures in 700 hours, I have now mounted my sensor on the firewall - will see how long this one lasts.
ladibird
Looking at the sky
Posts: 5
Joined: Thu May 18, 2017 6:13 am

Re: Rotax 912 Oil Pressure Sensor Problem

Postby ladibird » Sat May 18, 2019 3:31 am

Seemingly, this is an old problem of oils sensors (sender units) on the Rotax engines. I have replaced maybe five units in 300 hours, as they start fluctuating then fail completely. I have now installed an auxiliary switch with a warning light. Two ideas here. Senders dont like viabration and heat. Having a high heat issue with the cowling / ducting on the original design was solved when the front end was repaired / replaced. Apparently, the sender units dont like to exceed the 100 degree C limit, and this resulted in multiple replacements. Since the front end repairs, the sender unit has lasted much longer. Also heard that engine vibration causes failure, but the extension kit to mount the unit to the firewall is well into the 3 grand arena. Maybe an 80 buck sensor and a drum of fuel is more in the spirit of aviation
Flight of the miskruier
mythbuster007
Heard about flying
Posts: 2
Joined: Fri Aug 16, 2019 1:16 pm

Re: Rotax 912 Oil Pressure Sensor Problem

Postby mythbuster007 » Thu Feb 29, 2024 3:39 pm

tigger_na wrote:
Thu Jan 02, 2014 9:42 am
Cheaper elsewhere for me, please. My VDO oil sender unit also broke, giving wildly erratic readings. Luckily I had previous experience with loose instrumentation cabling and decided to limp to the airport instead of making a precautionary landing. My life, so extended, was made miserable by VDO prices, so instead of forking out a thousand bucks for a new sender unit I bought an EQUUS sender unit for 80 bucks and spent the R920 so saved on fuel. The EQUUS also has a 1/8-27 NPT thread, but only a 0-7 bar pressure range, versus the VDOs 0-10bar. Since 7 bar is the maximum allowable oil pressure on a 912 UL, this is acceptable, for me at least.

Unbelievably EQUUS is not able to provide calibration data for their oil sender unit model 9832, so I checked the resistance versus pressure by connecting the sender to a compressor and recording the resistance readings at various pressures. The results are below. Please bear in mind that the calibration was done with backyard (not calibrated laboratory) equipment. It is evident that, if the EQUUS is used as a straight drop-in replacement, your deviation in the relevant range 2-5bar range will be a maximum of 13%, which is really good enough for me. My MGL Odyssey allows me to define any linear pressure-resistance characteristic, so the error of the EQUUS drops to below 8%. Even better.
Do you know what the resistance in Ohms was set to on your EFIS (I have the same EFIS) for the Equus out of interest sake? I am busy doing some validations before I spend 6K on a pressure sensor on the 912is... Thanks!

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