Oil pressure sender

There is nothing special about the senders.
The sender is a variable resistor.
Zero  = 10 Ohms,  Max = 184 Ohms.
Max could be either 5 bar(80psi) or 10 bar(150psi).  
10 Bar is more common.
As long as the Resistance and Max range match, it should work.
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Why do you think you need a new sender?
What do you have against VDO?
No matter what brand name is on the case it was likely made in the same factory.
Aircraft Price = $60
Auto Parts Price = $40
eBay price = $30.
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Pay attention to the threads!!!
1/8 NPT and M10x1 look almost identical and are easily cross threaded.
Rotax has changed the threads on the Oil pumps over the years.
Be sure you know which one you have.

Bill -- Has does one determine what kind of threads (e.g., 1/8" NPT vs. M10x1) are used on their specfic 912's oil pressure port?  Is it listed somewhere in the engine's spec sheet or does one need to get a thread guage?

I would measure them. (Carefully)

The M10 x1 is 10mm(0.394") in diameter for the length of the straight threads with 1 thread per mm (25.4 threads per inch).

The 1/8 NPT is a tapered thread startiing with ~ 9.9mm( 0.390") at the end and widening to ~10.3mm (0.405") further up the thread.
The 1/8 NPT is 27 threads per inch (~1.06 threads per mm).

So you can see that they are within 0.01" of each other and easily confused.
Measuring the diameter at  two locations about a 1/4" apart should reveal the difference.
Same Numbers = M10;   Different numbers = 1/8 NPT.

Carefully attempting to thread them in will also reveal the difference.
Both will start to thread into the other for a few turns.
If you feel binding after 2-3 turns you have the wrong threads.  Stop!!!

The M10 is the more recent and common Rotax thread.
1/8 NPT to M10 adaptors are readily available from the Automotive World as most newer engines are Metric and most replacement Senders are NPT.

Hi Bill,

I've a Honeywell 3rd generation oil pressure sensor-Rotax # 956413. I noticed three wires red, black, white. The plane came with a VDO 350-010-021 oil pressure sender: 0-100 PSI; 10-184 ohm; 12v oil pressure gauge that has two terminals. Are these two compatible? If so, am I correct in using red to 12v, white to signal and black to ground? With plugs out and engaging starter I've no oil pressure.

I'm thinking a new VDO sender would be my best option, however, I can't seem to find any matches to VDO guage 350-010-021. Maybe a VDO sender that is 0-100 PSI; 10-184 ohm;  1/8 NPT-27; 12v oil pressure gauge that has two terminals is ok?

Thanks for your time,

Robert

The problem with all these gauges and senders is that they are not standardized and you can't  tell the players apart without a program, and they don't publish the program.

A one wire sender is Signal with the case being the ground.  The easy one!
A two wire sender could be Signal and Ground or... Signal and a Warning Lamp Switch with the Case being Ground.
The three wre sender is probably a Voltage output sender, With a very slim chance it is Signal, Ground, and a Warning Lamp Switch with a floating case.

CONFIRM:  Three Wires on the Sender, or Three Wires on the gauge???

And then there are all the different Pressure ranges with the various output Resistances, Voltages, or Currents.
Without going over the data sheets (If you can even find them) carefully,  it is best just to bench test them to see that you really have.

It seem like every manufacturer makes a meter and a matching sender  and keeps the details secret so you have to come back to them for parts.
It is a mess!

Even Rotax has Obsoleted the 956413 Sender and changed the threads in the Oil pump from NPT to M10 in the Process.

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