C182A oil pressure indication issues

timwinters

timwinters

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So, my oil pressure gauge started wagging out over the winter. I have a UBG16 w/an oil pressure probe as back up so I know it's an indication problem with the OEM gauge and not an actual oil pressure issue. The OEM gauge is an electric gauge with a "oil pressure transmitter" mounted to the side of the engine case.

The gauge typical reads correctly at start up and then sometime later (time varies) it starts fading. I could occasionally fix it by tapping on it so I assumed it was the gauge itself. It also might start reading correctly again on its own later in the flight...maybe not. The gauge was old and ugly so I thought, "what the hell, I'll replace the gauge, if it fixes it then great. If it doesn't, well, at least I now have a decent looking gauge."

So, I bought a new one from preferred airports, had the A/P change it out, nope, that wasn't the problem.

I changed my oil a couple of days ago and ran a new temporary wire from the transmitter to the gauge as a test to see if maybe it was a chaffed wire issue. Nope, that wasn't the problem.

So, I assume it has to be a transmitter issue since that's the only thing left. Problem is it's no longer available and I can't find one used (yet) either. Cessna PN is 0726109-1.

Questions & Help Requests:

1. Anyone have one laying around? Know of a used one available anywhere?

B. Anyone know if another transmitter might be compatible with this gauge. Aircraft Spruce has a couple:

VDO-oil pressure sender, 10-04183, $254.95

Cessna-P265-5037-oil pressure sender, 06-03035, $555

I have a call in to AS and have left a message for their "product specialist" but haven't heard back.

III. Anyone know if these units can be worked on, overhauled? And, if so, who?

d. Anyone know why I'm flying a 60 year-old airplane and expecting to find OEM parts for it?
 
timwinters said:
d. Anyone know why I'm flying a 60 year-old airplane and expecting to find OEM parts for it?
Click to expand...

a) because an equivalent new plane with readily availble OEM parts costs $700,000+;
b) it's made out of plastic;
c) they installed the wing in the wrong place;
d) all of the above.
 
Skywagon City is my go-to for used parts. An engine overhauler might have a couple laying around. There must be a cross reference for a newer part number. Ask Continental.
86 the old gauge since you already have a modern replacement?
 
Stewartb said:
86 the old gauge since you already have a modern replacement?
Click to expand...

My version of the UBG16 is older, before they were STC'ed as a primary (at least I think they're now approved as a primary). But, more importantly, this gauge is part of a modular 4 pack of gauges. Left Tank, Oil Press, Oil Temp, Right Tank. I'd hate to blank any one of them off...it'd look like chit.

Thanks for the heads-up on Skywagon City, I'll call them right now.

And @Bell206, thanks for the Yingling lead. I *think* I've already spoken with them but don't recall for sure...I've called so many.
 
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Just a hack idea but have you considered testing the output of the EI pressure transducer to see if it would drive the gauge?

And according to the STC, the UBG-16 has never been certified for primary. Hey, at least the price has always been right for what it does. I have fuel flow on mine along with all the cylinder, exhaust, and turbo temperatures.
 
try to provide a better ground for the gauge. with it varying it sounds like it is squirming around and varying the resistance to ground.
 
Tom-D said:
try to provide a better ground for the gauge. with it varying it sounds like it is squirming around and varying the resistance to ground.
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Thanks, Tom,

That sounds reasonable. There is a ground strap that connects to an adel clamp wrapped around (what I presume to be) the NPT fitting. I removed and replaced it when I removed the transmitter the other day to check for any noticeable blockage. The other end of the strap is under an oil pan screw and the engine is grounded to the frame with a hefty strap, but I didn't check those, I will.

I've called:

Skywagon City
Yingling
Texas Air Salvage
Air Salvage of Dallas
Dawson
Wentworth
Enparts
and Preferred

A couple are looking, but no success yet.

I've also called a couple of overhaul shops.
 
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I'd solder a wire to the case, and go to a good ground
 
Skywagon City just called me back. They said this style of oil pressure set up was only used for 1.5 years. All of 58 and the first half of 59. Hence the rarity. He said he'd sell me a capillary gauge for less than $200 and I'd need to run a pressure line to it...

Sounds like a decent plan if I can't find this transmitter and Tom's grounding ideas don't help.
 
timwinters said:
He said he'd sell me a capillary gauge for less than $200 and I'd need to run a pressure line to it...
Click to expand...
If you end up doing that, remember the fitting that replaces the pressure transmitter is not just an ordinary fitting.
 
Beegles saved my bacon when a cowl flap came from together last year. They were one of two places on earth that had one. The other one was 15 times the price from Texas Air Salage (not kidding). Might give 'em a call.

http://www.beeglesaircraft.com/
 
Tom is on the right track. Run a small wire from the pressure transducer, or to a case bolt real close to the transducer, all the way to the gauge's metal case. That's the only way to eliminate the stray currents from the alternator's ground flow from affecting the gauge indications. Cessna found that they had to do this with their oil temp retrofit kit: https://www.google.ca/url?sa=t&rct=...?as_id=29648&usg=AOvVaw1x3Zu6lJf3W_UIKkQHFs2M

Paragraphs O and P on page 3.

When the alternator is charging, it's pumping electrons into the engine case. That case is grounded by ground straps to the engine mount, which is grounded to the firewall. Old stuff oxidizes and small resistances start appearing at those connections. Oil contamination, heat and vibration don't help. That alternator flow, being rather large, causes voltage drops at the connections, and the flow starts looking for other ways to ground. It finds it in engine control cables, tach cables, primer lines, whatever. And it finds a path via the oil pressure or temp transducer, through the thermistor in the transducer, through the wire from the transducer to the gauge. The normal, proper flow is between the transducer and gauge, and more flow means a higher indication. If the alternator is pushing electrons everywhere it finds a path, it drives the gauge higher by boosting the flow through the gauge wire. The separate ground wire between the transducer and gauge case neutralizes that by removing whatever potential the other resistances are causing.

So you start up and take off. The alternator is busy recharging the battery, so flow is high. The gauge could read high. Once the battery comes back up to snuff, the current tapers off and the gauge reading drops some. If there are loose engine/mount/firewall ground connections, the gauge experiences varying flow, making the needle jumpy. You turn on a landing light or two and the gauge goes nuts again. Lots of weird readings. Electricity is so much fun!

Those old airplanes often had rubber bushings in the firewall. The mount bolts went through the mount and a ground strap at each bushing. The rubber ages and shrinks and crumbles and the bolt tension disappears and the ground straps are loose. We've found those straps missing altogether.
 
Well,

I guess...

Since I ran a temporary new wire from the transmitter to the gauge on the positive side, and didn't remove the old wire, I can hook it up ground-to-ground as a test. That'd be really easy, the wire is there. Thanks, Dan

Just one thing. You said:

Dan Thomas said:
So you start up and take off. The alternator is busy recharging the battery, so flow is high. The gauge could read high. Once the battery comes back up to snuff, the current tapers off and the gauge reading drops some.
Click to expand...

My gauge doesn't just drop off a bit. It goes to zero. Past zero actually.

Also, regarding ground straps and aging and deterioration. All my ground straps are only 2 years old, everything was replaced at overhaul. An additional heavy gauge "jumper" from engine to frame was also installed.
 
Tim,
I have a similar system in my C182B, can you tell me where your oil pressure sender for the UBG 16 is hooked to the engine?
 
ZK Kiwi said:
Tim,
I have a similar system in my C182B, can you tell me where your oil pressure sender for the UBG 16 is hooked to the engine?
Click to expand...
We removed the OEM transmitter from the side of the case and installed a short hose with a "T" fitting at the end. The OEM transmitter is screwed into one side of the "T", the UBG 16 transmitter into the other.

Worked well for a dozen years. :(

As a general comment, I ran by the hangar yesterday and installed new/additional ground wires on the transmitter and gauge. I haven't flown it yet, and I'm not holding my breath that this will fix it, but we'll see.
 
Update.

Still acting up.

My new mechanic at LBO thinks it's a grounding issue also since it's intermittent. Specifically, he thinks it's an issue with the ground "tab" on the gauge.

Colorado Airparts texted me a photo yesterday of a transmitter with a quick "are you still looking for one?"

"Hell yeah!" was the answer. I mean, they're not available any longer, and mine's presumably 60 years old, so, if they got one I'm buying!

I called. "How much you want for it?"

"$500. We got it in a box of random parts that we bought and it looks like it's new, never installed."

<pause> "That's a bit salty."

"Yeah, I'm just kidding, how about $75?"

"Sold to the Catholic boy in Missouri!"
 
We installed the new transmitter today, I then flew it for 0.7 and the pressure was rock solid.

I think it's fixed. Since it started acting up, the gauge has never worked for over 10 to 15 minutes at a time.

Thanks to everyone for the input.
 
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Hi,
Would you mind to send photo of the sender?
I have the same problem and going through the same path.
thanks
 
Eliran said:
Hi,
Would you mind to send photo of the sender?
I have the same problem and going through the same path.
thanks
Click to expand...
Hi, Eliran,

I sold the aircraft a couple on months ago. But it looks very similar to this unit:

2671E70B-2B6B-4265-B78C-FF52BED1122C.jpeg
 
Thank you so much.
It’s big help!
 
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