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Here is a stupid question!

Located on the passenger side of the engine, below the carb and below the last cylinder, close to the bottom of the block is an oval sensing unit covered with black rubber held together with a spring and at the outer end there are two electrical terminals, the wires have since come off. What is it? Some sort of oil pressure gauge?
 

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Hey, go easy on the Canuck Opel Newbie! He's a Federal Government employee in our nation's capital. And might have the ability to aim our Canadarm Phaser Cannons at people who 'dis him! (and you thought it was just some trivial mechanical arm that we supplied on the Space Shuttle and International Space Station?)
 

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Graham,

I should have added that you really should get it wired back up. You don't want to risk not knowing that you've lost oil pressure...

-Travis
 

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Oil Pressure Sending Unit Connections

I guess we're back to being serious again...

One terminal should be labeled "G", and has a retaining nut. This connects to a light-blue w/ green stripe wire, and provides a variable resistance to the oil pressure gauge. It connects to the gauge connection also marked "G".

The other terminal should be labeled "WK", and has a spade connector. This connects to another light-blue w/ green stripe wire (why are both wires the same colour? Anybody?) that connects to the indicator (idiot) light in the oil pressure gauge.

I never noticed before that both wires (at least in the wiring schematic) are the same colour. But they connect through different wiring harness connectors, and go to different connections on the oil pressure gauge. I presume that the sending unit has two functions; a variable resistor for the gauge, and a "switch" for the light. Is that true? Why did Opel use the same wiring colour for both connections? Or are both terminals the same function?

Take good care of that sending unit. Replacements are difficult to find (Gil at OGTS occasionally has stock), and NOS units show up on ebay sometimes, but are always expensive. Typically $100 USD!!!
 

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Huh! I never really gave it much thought. I didn't know they costed that much. Heres a possible idea if it doesn't make a difference which wire goes where. Put a brass tee in place of sender and use two single senders in place original. Any thoughts?
 

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Re: Oil Pressure Sending Unit Connections

kwilford said:
Why did Opel use the same wiring colour for both connections? Or are both terminals the same function?
Maybe they figured it was enough to use different connectors on the ends. Strange!

-Travis
 

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one a switch, the other a rheostat

One terminal is used to ground the switch for the light. It is the terminal marked "WK." All cars with idiot lights have one of these, and for the most part they are interchangeable, so if you only want the idiot light (or if you have a Kadett or Manta without a pressure gage) get one for a VW when you need a replacement and you'll only be out $14.

The other terminal, marked "G," is for a rheostst that has a change in value for a change in input pressure. To the best of my knowledge, all VDO gages have and still use the same scale for resistance vs. pressure, and you should be able to replace yours with the one from any car equipped with VDO gages. These electric pressure gages should be viewed with some suspect, however, as they tend to drift over time and they are the lowest rung in the accuracy food chain.

If you want to test yours, and are feeling ambitious, I can detail the rig you would need to test/ calibrate the gage and sender. Either contact me directly for details or clammor-up and I'll post the procedure somewhere.
 

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Enlighten Us, Wise Old Oldopelguy

Oh gracious Old Oldopelguy, please share your learnings with us. Please post the procedure as it was passed down from the top of of the mountain, and the Moderator (yours truly) will move a copy to the FAQ section.

While you're at it, any idea why Opel used the same colour wires for both terminals? It seems odd that two connections, side by side, with very different functions, should use the same wiring code. The Opel Engineering guys must have had a lot of faith in the correct terminal ends staying in place for the life of the car!
 
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