Scary High Oil Temps - Lycoming 540

[WDD]

Crimp worked better than solder and shrink tubing?

 

[EdFred]

I installed myself as well and really like the instrument and ease of installation. I removed all of my old analog gauges in the process. Accurate fuel level metering and fuel calculation add immeasurably to safety.

But I had the same connection failures on a couple of probes. One EGT probe was giving me a particularly bad time, only lasting a few hours after each of my numerous attempts to address it. I even had staggered the connectors as you mention, and tried adhesive heat shrink on the individual wires as well as around the bundle, but I still suffered failures. After contacting EI for a solution, they sent me a kit with ferrules and a crimp tool to try (mentioned in another thread), and I haven’t had a failure since.


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I started with heat shrink, but being next to the engine...

 

[WDD]

I started with heat shrink, but being next to the engine...

It was that much that it deteriorated a solder connection? I wouldn't have thought. And that's why I still learn a lot from this place.

 

[EdFred]

It was that much that it deteriorated a solder connection? I wouldn't have thought. And that's why I still learn a lot from this place.

No solder connection. But the heat shrink deteriorated and the wires started to move around in the air in the cowl and I got a loose wire from the movement.

The not so pretty, but effective solution for me:

 

[Salty]

I put zip ties on either side and supported them nicely, you name it. None of that worked if they weren't tightened just right. I actually had a friend install the connectors initially and he went really hard on all of them at first which was the real problem. Then, on a couple I fixed, I went too loose, so they fell out. Eventually I found the right torque to put on the set screws and stopped having issues.

 

[mondtster]

Using some real thermocouple connectors would likely solve most of the problems with connections like this.

 

[bnt83]

No solder connection. But the heat shrink deteriorated and the wires started to move around in the air in the cowl and I got a loose wire from the movement.

The not so pretty, but effective solution for me:

View attachment 131719

That hi-temp silicone rescue tape works great on stuff like this.

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[Mike Gagnon]

I didn't even know those Ferrules existed! I need to try one of those kits.

Wire Connector Package | Electronics International | Aircraft Engine Instruments

Improve Your Connection Reliability with Crimpers and Ferrules Improve Your Connection Reliability with Crimpers and Ferrules Avoid Common Wire Connection Issues

iflyei.com

Sent to me for free after I contacted them. I’m glad they eventually came up with a solution that worked for me, and didn’t charge me for the fix. Good customer service.


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[WDD]

I follow this guy's South Main Auto Repair YouTube videos. Lot's of facts and details, etc.

Here is a nice video on electrical connector crimping. Yep, geeking out here.

 

[SixPapaCharlie]

I am coming back to this thread with a bit more education.

First thing, I thought I would go to KOSH, buy an engine monitor, and hand it to my mx and say "Install this now thank you"
Turns out it takes 5-6 weeks for them to configure it after you fill out all of the paperwork.

In the meantime, I have an oil temp gauge in the panel that is doing its job.
For all of you that said "Sounds like a grounding issue", You appear to be correct.

When we installed the new gauge, we ran it to a 12v power source and grounded it to the same place as the original was ground and the behavior was erratic.
We attempted to ground it to a different location on the panel where a few other things were grounded but that popped a breaker.

My MX said "we are going to eliminate the panel completely" and did a test running a really long wire back to the battery + and one to the - and boom it read 120 degrees which made more sense as the engine had run about 15 min earlier.

I guess that told him what he needed to know in addition to a lot of ohms testing with a multimeter and other wizardry.
Now as I understand it, the + wire is connected to a new location and the - wire is grounded to the engine block and it is working beautifully.

All of this is moot because in a few weeks I will get a box in the mail and I will hand it to my mechanic and say "Install this thank you"

He threw a lot at me "Could be corroded connections, dirty connections, wires going bad, something else sending power back through the ground" and some other phrases.

So let's say I didn't acquire an engine monitor and wanted the old gauge to work. How (Like I am a 5 year old) would I go about finding out what is the real problem?
And some smart person probably already told me this up there ^^^ but I have a cluster of gauges that appear to be getting a 12v power input on the ammeter gauge and the remaining 7 gauges are daisy chained down stream from that one, and there appears to be a ground on the last gauge that is connected to a sheet metal screw in the back of the gauge cluster housing.

Much like when I was in college playing Mortal Kombat where I would just mash buttons randomly not knowing what I was doing, I took the Multi meter and set it to ohms and put the red one on the 12v supply and touched random spots on the airframe and consistently got 6 Ohms. Is that good? bad? Sometimes I would win Mortal Kombat but I am not sure I am winning this.

I guess the question is what would someone that really knows the real special Mortal Kombat combos do to isolate where in the gauge chain the problem lies?

I thought about just replacing all of the wires or scrubbing the connections with a wire brush but that would just be mashing random buttons hoping for a "FATALITY!"

 

[SixPapaCharlie]

When I say "Daisy chained", here is what the back of the cluster looks like

 

[flyingcheesehead]

For all of you that said "Sounds like a grounding issue", You appear to be correct.

Glad you found it!

So let's say I didn't acquire an engine monitor and wanted the old gauge to work. How (Like I am a 5 year old) would I go about finding out what is the real problem?
And some smart person probably already told me this up there ^^^ but I have a cluster of gauges that appear to be getting a 12v power input on the ammeter gauge and the remaining 7 gauges are daisy chained down stream from that one, and there appears to be a ground on the last gauge that is connected to a sheet metal screw in the back of the gauge cluster housing.

Much like when I was in college playing Mortal Kombat where I would just mash buttons randomly not knowing what I was doing, I took the Multi meter and set it to ohms and put the red one on the 12v supply and touched random spots on the airframe and consistently got 6 Ohms. Is that good? bad? Sometimes I would win Mortal Kombat but I am not sure I am winning this.

I guess the question is what would someone that really knows the real special Mortal Kombat combos do to isolate where in the gauge chain the problem lies?

Electrical problems are a giant pain. And I have a degree in EE so theoretically I know a few things.

Recently, I was trying to diagnose an apparent electrical issue on my tractor, and the neighbors were probably laughing because I was driving around with wires coming out from under the hood with a multimeter taped to the dash. It didn't help. And I spent far too much time examining wiring diagrams that show electrical connections, parts manuals that kinda showed where the wires physically went to some extent, and sitting there staring at and labeling things as I found them on the tractor itself and correlated them with the diagrams.

Multimeters are limited in their usefulness sometimes, although that whole "6 ohms everywhere" thing sounds highly suspicious to me, like there is something wrong with the meter. Does it read 0 if you touch the leads to each other?

The issue with multimeters is that a lot of electrical stuff has transient changes that don't show up when reading DC, and you'd never see unless you were using an oscilloscope. Even then, sometimes they won't happen unless the right combination of heat, vibration, and who knows what else are in play.

Since it sounds like you have an A&P who actually gets electrical stuff to some extent - Keep him happy. Many A&Ps are not very good at electrical stuff. Even those that are good, there is a certain amount of voodoo involved in GA electrical troubleshooting. There may be wiring diagrams, but who knows what might have been changed in the last 50 years, and that might involve a lot of tracing of things. You never know what you're going to find on an old airplane! I think my favorite was when we were having problems with the club's 182 stall/gear warning system. Shop pulled the overhead pieces in the interior to get to it, only to find a handwritten note stating it had been moved to the firewall! At least they told us where it was...

 

[Capt. Geoffrey Thorpe]

6 Ohms between the 12 volt supply and the airframe ground is just the impedance of all the gauges and stuff connected between the two points. You want to find issues (resistance) between the ground at the gauge and the ground at the sending unit. The problem is you are looking for fairly small numbers - it may be easier to find a voltage drop across a specific connection when the engine is running and the alternator is charging. Look for resistance (with power off) or a voltage (with the engine running and charging) between a ground behind the panel and the engine case for starters. If you find something - check some place in the middle until you narrow it down.

Is there a difference in the indicated oil temperature reading with the engine off and the engine running / charging?

 

[bnt83]

One engine monitor wiring management idea. (For your new engine monitor)

 

[Chip Sylverne]

IMHO, cleaning all grounds from the battery connection to the alternator and (+) at the buss bar isn't mashing random buttons, but good maintenance, and something you should do anyway before replacing your analogue with digital stuff.

Clean connections never hurts. Only cost is time and tedium.

 

[JEM68]

One engine monitor wiring management idea. (For your new engine monitor)

View attachment 133490

I installed my own CGR-30 combo, but it doesn't look that nice. Another advantage of an engine monitor is geeking out on all the data it records. It's easy to download and analyze. Also, you can have the alarm limits changed, such as CHT, by completing a form and having an A&P sign it and email it to EI.

 

[Dan Thomas]

Now as I understand it, the + wire is connected to a new location and the - wire is grounded to the engine block and it is working beautifully.

Yup. Way back in post #13 I said all this:

A poor engine ground to the airframe can do it.

If the alternator is not well-grounded to the airframe, those electrons from it like to find other paths to the airframe, and one of those paths is through the oil temp sensor and to the gauge. This increases the electron flow through the gauge, spiking it.

In old airplanes, there are plenty of places where grounding is less than optimal, and so the new electric gauges in the old airplanes would read falsely high. The fix was a length of 20-gauge wire and some terminals to attach it to the engine crankcase as close as possible to the temp sensor, usually at an accessory case stud and nut, and then to the gauge's metal instrument case. This removed the voltage differential caused by bad grounding and the gauge would (usually) smarten up.