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Darren S

Well Known Member
I didn't build my -7. I am changing the instrumentation to an Advanced 3500. The new Oil Pressure and Fuel Pressure senders, that Advanced sent me, don't fit on the transducer, where the old ones were.

I want to mount them facing forward. Currently on the Transducer is this Gold and Black sender. I have no idea what it is for. I want to remove it and place the Oil pressure sender in it's spot.

Does anybody have an idea what this little unit does ? Here's a pict.

Thanks and Happy Thanksgiving to all y'all south of the border :)

Darren

GoldandBlacksenderontransducer-1.jpg
 
Darren S said:
Does anybody have an idea what this little unit does ? Here's a pict.

Thanks and Happy Thanksgiving to all y'all south of the border :)

Darren
Click to expand...

Oil. Could be for an idiot light or gauge. When you follow the steel braided line that goes to this sensor, what do you find it attached to? This would be an important clue.
The one below looks like a fuel line passing through it.
Assuming the oil line steel braided is actually feeding this sender, the open port you have shown would cause a problem.
 
That's an oil pressure "switch", generally used for an idiot light or hobbs.
 
Clarification of terminology.

The "sender" IS the "transducer".
The sender/transducer is mounted on a "manifold".
 
That looks exactly like the SPDT oil pressure switch that I have sitting on my desk. Mine came from B&C, but is made by the Hobbs company (p/o Honeywll I think). The B&C part number is 58012.

http://www.bandc.biz/pressureswitchspdt.aspx

It has 3 terminals - common, NO (normally open) and NC (normally closed). I think the switch moves at a few psi.

If you have an extra spot on your manifold, you can have both an oil pressure sensor (drives EFIS/EIS or guage) and an oil pressure switch (drives Hobbs and idiot light). That's what I'm doing.
 
You're looking at the oil pressure switch. The switch closes when oil pressure is sensed. Usually used to operate the Hobbs. There should also be an oil pressure sender. The sender will sense the oil pressure and send a signal to your oil pressure gauge.

So on the firewall mounted manifold, you should have an oil pressure line coming from your engine to the manifold, and then the oil pressure switch, and the oil pressure sender.

To make the sender fit on the manifold, you can use an AN915 fitting. This is a 45* fitting to offset the sender from the firewall.
AN915C.jpg


The other ports on the manifold can be used for fuel pressure or other pressure sensors.
 
The little white sticker at the top of the picture does say "Hobbs" so you guys are all on the right track.

I have a conventional Hobbs meter like this.

http://www.aircraftspruce.com/catalog/inpages/hobbs.php

I thought it ran off the Master Switch. I hear it clicking away even when the engine isn't running.

This Gold/Black sender runs the Hobbs meter also ? If it does, can I bypass it somehow so I can use it's spot.

Thanks again for the help.

Darren
 
If the hobbs is "clicking away" with the master switch on / engine off, you might want to troubleshoot that a little more.

Your oil pressure switch should be checked with a multi meter to see if it's stuck in the closed position. ie does it show zero resistance across the two terminals? If it shows zero resistance, get a new oil pressure switch, such as the one posted earlier by IowaRV9Dreamer.

On the other hand, the previous owner may have wired around the oil pressure switch. Again, you should check it out to see exactly what you have. A correct wiring path would be as follows...

<Ground> to <Oil Pressure Switch>
<Oil Pressure Switch> to <Hobbs (-)>
<Hobbs(+)> to <Fuse Panel>

edit: Looking at the photo you posted, the wiring may be a little different than the wiring path I listed above. Your photo shows terminal boots covering both of the terminals on the oil pressure switch. Terminal boots are typically only installed on wires/terminals that see 14/28Vdc. So your wiring path may be as follows...

<Ground> to <Hobbs (-)>
<Hobbs(+)> to <Oil Pressure Switch>
<Oil Pressure Switch> to <Fuse Panel>

end edit:



Bottom line is that the standard installation usually includes both the oil pressure switch AND the oil pressure transducer/sender.
 
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Thanks for the help Scott, I will check the wiring as you suggested but I like your idea of using the 45* elbow. I'll likely go that route.

Darren
 
Yes, that is the manifold that Van sells.

They are fabricated from aluminum. The early versions were not coated, but later versions have the blue color.
 
Van's Manifold

Hi Marc
Got one of the new ones, real nice, I like it..:D

RV in hibernation til spring...got about 6-8 inches of snow today and it's still coming down..:(

Cheers

Bruno
 
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