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  #21  
Old 10-26-2012, 06:07 PM
sandpiper sandpiper is offline
 
Join Date: Nov 2009
Location: Independence, OR
Posts: 317
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Quote:
Originally Posted by MartySantic View Post
Jerry,

Everyone seems to be pointing to the sensor even though the mechanical gauge showed the same.

Suggest removing the oil pressure regulator components and examining. Simple to do.

Try posting your issue on CTFlyer, Engine/Rotax forum. Potential assistance there also.

It's ctflier. If you use ctflyer you get a defunct site if it comes up at all.
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  #22  
Old 10-29-2012, 09:59 AM
Catbird Catbird is offline
 
Join Date: Oct 2009
Location: Birmingham, Alabama
Posts: 135
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Well . . . I solved it.

Friday afternoon at the hangar I reached in behind the engine to jiggle the two spade connectors coming from the nefarious oil pressure sensor. Nothing violent or extreme; just a jiggle to show a friend which connectors were to be inspected. To my surprise, the red sensor wire immediately broke off at the entry to the crimped barrel of the connector. It must have been hanging on by a single strand. The wires coming from the sensor are multi-stranded 22 gauge, or possibly even smaller. I suppose vibration had taken its toll. Another contributing factor is that I was using a single crimper tool and not applying a second crimp at the end of the barrel to secure the wire insulation. Later in the project I had purchased a double crimping tool, but had not bothered to recrimp these connectors since they were 'hidden' down behind the engine. After reworking the wiring from the sensor to the D-sub connector behind the panel, my Dynon oil pressure reading is solid and relatively stable.

I apologize for the false alarm. Now if I can only find a way to blame my amateur crimp job on that Honeywell oil pressure sensor...
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  #23  
Old 10-29-2012, 10:37 AM
Dave12 Dave12 is online now
 
Join Date: Oct 2010
Location: Elkton, Md.
Posts: 1,745
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Hi Catbird, I had that happen while flying last winter. I was at 4500' and the pressure went to zero. Under normal circumstances I think most will agree that this situation is serious. I never gave it a third thought, I knew it was "that sensor" or it's associated wiring.
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  #24  
Old 10-29-2012, 12:12 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,662
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Quote:
Originally Posted by rvbuilder2002 View Post
Considering the number of instrument indication problems I am aware of that were caused by wiring connection issues, my bet would be that is very likely the cause of this issue also.
Quote:
Originally Posted by Catbird View Post
Well . . . I solved it.

Friday afternoon at the hangar I reached in behind the engine to jiggle the two spade connectors coming from the nefarious oil pressure sensor. Nothing violent or extreme; just a jiggle to show a friend which connectors were to be inspected. To my surprise, the red sensor wire immediately broke off at the entry to the crimped barrel of the connector. It must have been hanging on by a single strand. The wires coming from the sensor are multi-stranded 22 gauge, or possibly even smaller. I suppose vibration had taken its toll. Another contributing factor is that I was using a single crimper tool and not applying a second crimp at the end of the barrel to secure the wire insulation. Later in the project I had purchased a double crimping tool, but had not bothered to recrimp these connectors since they were 'hidden' down behind the engine. After reworking the wiring from the sensor to the D-sub connector behind the panel, my Dynon oil pressure reading is solid and relatively stable.

I apologize for the false alarm. Now if I can only find a way to blame my amateur crimp job on that Honeywell oil pressure sensor...
Thanks for providing the follow up info to confirm what the actual cause was.
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  #25  
Old 10-30-2012, 08:19 AM
Catbird Catbird is offline
 
Join Date: Oct 2009
Location: Birmingham, Alabama
Posts: 135
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One more clarification:

The wires coming off the Honeywell oil pressure sensor are actually 24 gauge standed. These are probably the smallest or lightest wires on the entire plane, and by virtue of their smallness, pose a real challenge in attaining a durable and reliable crimp connection. I'm not saying that anything should be changed. I'm just saying that these crimp connections should be done very carefully and the wires AND spade connectors should be securely anchored to obviate the risk of breakage due to vibration or movement.
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  #26  
Old 10-30-2012, 08:44 AM
Dave12 Dave12 is online now
 
Join Date: Oct 2010
Location: Elkton, Md.
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Catbird, check pm's
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  #27  
Old 10-30-2012, 05:31 PM
BigJohn BigJohn is offline
 
Join Date: Nov 2008
Location: Gloversville, NY
Posts: 1,588
Default Another technique

Here is the way my friend Bill (A&P, IA) makes connections like this, and I have used the technique on a couple of especially sensitive areas. He uses an uninsulated spade (or whatever) terminal. Doubles over those really small wires and crimps, then solders. Then slides appropriate size of shrink wrap over the terminal and wire for an inch or so and shrinks to provide mechanical strength. Seems to work well. I'm interested in what you real experts think of this method.
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  #28  
Old 10-30-2012, 10:50 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,662
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Quote:
Originally Posted by BigJohn View Post
Here is the way my friend Bill (A&P, IA) makes connections like this, and I have used the technique on a couple of especially sensitive areas. He uses an uninsulated spade (or whatever) terminal. Doubles over those really small wires and crimps, then solders. Then slides appropriate size of shrink wrap over the terminal and wire for an inch or so and shrinks to provide mechanical strength. Seems to work well. I'm interested in what you real experts think of this method.
Not saying that soldering is universally wrong, just that done improperly it can cause more problems than it solves.

The death to small wires is repeated bending concentrated at a small localized point. This doesn't have to be a lot of bend, just the small repeated movement induced by vibration.
The reason good quality connectors have two crimps, is the second crimp is a strain relief for the wire. It clamps on the insulation so that any bending /vibration is induced into the main body of the wire, not just the conductor strands.
The problem with soldering, is it is very easy for solder to wick under the insulation along the strands of the wire. This makes this wire very stiff. If this stiff area falls outside the strain relief crimp of a connector, you have a new bend concentration point where the conductor can now fracture beneath the insulation and be very hard to detect.
Covering with heat shrink helps, but it is still somewhat flexible so doesn't totally solve the problem.
I personally would never solder a connector on a wire that could be exposed to vibration (where on an airplane wouldn't they), unless the entire portion of the wire in the area of the connector can be solidly anchored so there is no possibility of movement (and if you do that, an unsoldered one will probably survive just as well).
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  #29  
Old 12-02-2019, 01:23 AM
dpemmons dpemmons is offline
 
Join Date: Apr 2017
Location: San Francisco, CA (KDVO)
Posts: 50
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I recently lost oil pressure indication in my 320 hr, 2009 D-180 RV-12. Two weeks ago on my way to the Amboy Fly-In from the SF bay area, just south of Bakersfield as I was climbing to cross the Tehachapis before a planned fuel stop at WJF I noticed the indicated oil pressure drop into the 20s before recovering to normal levels. This happened a couple times again in a rapid succession a few seconds apart, each time dropping further into the red. That certainly got my attention so I turned around toward Bakersfield Municipal where I landed without incident. By the time I got there I'd been flying with zero indicated oil pressure for maybe 5 minutes. There were no other symptoms. My friend (who was also going to the fly-in) was by coincidence nearby and picked me up in his Mooney and we continued the trip.

This weekend I returned to Bakersfield by car. I drained the oil, pulled the magnetic plug and found it clean. Replaced the Honeywell oil pressure sender with a VDO sender and purged the oil system. Probing the sender's resistance with a multimeter while turning over the prop by hand indicated I was getting oil pressure, so I rigged up a VDO gauge powered from the 12v plug in the cabin in order to completely isolate it from existing sensor wiring, EFIS, etc. That gauge indicated normal pressure. After an extended runup, a few high speed taxi tests and some laps in the pattern I flew home.

The sender had previously bounced around in flight when nothing else was changing, moving by 10-15psi or so in a few seconds but within the green arc. Knowing all the problems folks have had with the sender I already thought I should move it to the firewall at next annual. Now I certainly will.
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