EGT probe change?
- Thread starter swatson999
- Start date
skydancer
RV-7 O-360 CS Prop. Dual Skyviews/AHRS. TruTrak AP
Jake,
After you installed the new connectors, did you solder them?
After you installed the new connectors, did you solder them?
So we while we DO change subdle things about various parts, including EGTs over time due to vendor changes, small incremental product/quality improvement efforts, and other reasons, when a part number doesn't change, we expect all of the above to be functionally identical.
So for those of you that are seeing different temperatures at in-flight EGT temps, we're not sure if we're dealing with sensor aging, slight differences that shouldn't matter that do, or something else. We're investigating a number of different things here. This issue is made harder by the fact that some subdle changes are hard to tie to exact dates in the field.
One of the axes we're investigating is whether the connectors have any impact on the temperature. So for those of you that have, say , 3 original EGTs that show one temperature, but a newer replacement that is different:
1) Which exact EGT probe are we talking about here? There are 3 p/ns with 3 different hose clamp lengths. If you don't know that, just your engine type alone will be helpful.
2) One test that you can perform in the field that would be valuable to us: remove the connectors on both one of your old thermocouples and one of your new ones. In other words, join the thermocouple wire from the probe DIRECTLY to the EGT harness directly together, making sure that each end of the wires are physically touching each other. A butt splice is one way to accomplish this, but only the kind that allows physical contact between the wires (not the kind that has a metal block in the middle). This is the exact thing we're trying to remove from the equation - any non-thermocouple wire in the connection chain (it shouldn't matter in the case of connectors when there's no temperature change across them, but it's something worth exploring, even though we don't think this will end up being the root cause)
So for those of you that are seeing different temperatures at in-flight EGT temps, we're not sure if we're dealing with sensor aging, slight differences that shouldn't matter that do, or something else. We're investigating a number of different things here. This issue is made harder by the fact that some subdle changes are hard to tie to exact dates in the field.
One of the axes we're investigating is whether the connectors have any impact on the temperature. So for those of you that have, say , 3 original EGTs that show one temperature, but a newer replacement that is different:
1) Which exact EGT probe are we talking about here? There are 3 p/ns with 3 different hose clamp lengths. If you don't know that, just your engine type alone will be helpful.
2) One test that you can perform in the field that would be valuable to us: remove the connectors on both one of your old thermocouples and one of your new ones. In other words, join the thermocouple wire from the probe DIRECTLY to the EGT harness directly together, making sure that each end of the wires are physically touching each other. A butt splice is one way to accomplish this, but only the kind that allows physical contact between the wires (not the kind that has a metal block in the middle). This is the exact thing we're trying to remove from the equation - any non-thermocouple wire in the connection chain (it shouldn't matter in the case of connectors when there's no temperature change across them, but it's something worth exploring, even though we don't think this will end up being the root cause)
jakej
Well-Known Member
Jay
FWIW- I've never soldered any thermocouple wires.
Jake J
jakej
Well-Known Member
DS
Steve W made this comment - "Pretty much just like the one that went in, maybe a little bit of color change due to heat".
In other words, it was intact in appearance, but failing in operation." - that would indicate to me that most likely the actual probe has not failed but the connectors & crimping is an issue.
This is an idea that someone who is having issues may like to try - instead of using the push on type connectors why not try the pin & socket closed barrel type (crimped by using eg Daniels oe Astro crimper or similar) connectors then heatshink the joint. These work well too & I have used them in a Dsub firewall connector.
HTH
Jake
Steve W made this comment - "Pretty much just like the one that went in, maybe a little bit of color change due to heat".
In other words, it was intact in appearance, but failing in operation." - that would indicate to me that most likely the actual probe has not failed but the connectors & crimping is an issue.
This is an idea that someone who is having issues may like to try - instead of using the push on type connectors why not try the pin & socket closed barrel type (crimped by using eg Daniels oe Astro crimper or similar) connectors then heatshink the joint. These work well too & I have used them in a Dsub firewall connector.
HTH
Jake
swatson999
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- Oct 6, 2010
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After recrimping 3 times, and trying all new connectors, I have doubts that it was the crimp, but I could be wrong.
I basically just gave up and replaced it and the new one is working fine, just reading higher (the original question I had in this thread).
jakej
Well-Known Member
Steve
I understand the original question bit, maybe not all thermocouples are created equal
Did you by chance ever check your probe readings against a calibrated sensor ? If not then how do you know which is correct :-/
FYI - my comments were only generalisations & meant to be informative, hopefully, as there seems to be a lot of reading of this topic.
Jake J
I understand the original question bit, maybe not all thermocouples are created equal
Did you by chance ever check your probe readings against a calibrated sensor ? If not then how do you know which is correct :-/
FYI - my comments were only generalisations & meant to be informative, hopefully, as there seems to be a lot of reading of this topic.
Jake J
swatson999
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- Oct 6, 2010
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No, I never tested them against a reference source, as I don't have anything lying around in my garage which is calibrated to 1400 degrees F.
With EGTs, it's not really whether they're calibrated to absolute ground truth values, anyway...it's the relative values/change in readings that matter.
Thus, my question...all 4 were reading within 10 or so degrees of each other consistently for about 100 hours, then the #4 failed (again) and the replacement probe (which had different connectors) suddenly was reading 50 degrees or more higher than the other 3.
I'm pretty sure that cylinder didn't magically start running exhaust temps that are 50 degrees higher the very same day I changed the probes, so *it must be the probe which has changed* somehow.
I don't care if they did, I just want to know, because if they did for whatever reason (I *hope* it was to make them more robust), then I'll just change the other 3 at annual.
With EGTs, it's not really whether they're calibrated to absolute ground truth values, anyway...it's the relative values/change in readings that matter.
Thus, my question...all 4 were reading within 10 or so degrees of each other consistently for about 100 hours, then the #4 failed (again) and the replacement probe (which had different connectors) suddenly was reading 50 degrees or more higher than the other 3.
I'm pretty sure that cylinder didn't magically start running exhaust temps that are 50 degrees higher the very same day I changed the probes, so *it must be the probe which has changed* somehow.
I don't care if they did, I just want to know, because if they did for whatever reason (I *hope* it was to make them more robust), then I'll just change the other 3 at annual.
jakej
Well-Known Member
Steve
"..it's the relative values/change in readings that matter" -- I'm very aware of this
Bear with me on this, please.
Back on the 2nd Sept you mentioned a probe going to >1600F, I have seen them go to 2500 C which is impossible of course however it was a connector on the probe sidethat caused this high reading.
I mentioned using the calibrated method so as to determine if the probes themselves are actually at fault & that there is a difference in output values.
We know your CHT wiring loom has not changed but the probes have & therefore the termination in it may be different too.
Does the 'new' higher reading probe have a single or multistrand conductor ?
What colour is the connector on it ?
Just trying my best to help here
I know these sorts of issues can be very frustrating & wish that everything was just a simple plug & play scenario, but it is what it is & we have to sort it out.
BTW - what type/model of crimper are you using ?
Jake J
"..it's the relative values/change in readings that matter" -- I'm very aware of this
Bear with me on this, please.
Back on the 2nd Sept you mentioned a probe going to >1600F, I have seen them go to 2500 C which is impossible of course however it was a connector on the probe sidethat caused this high reading.
I mentioned using the calibrated method so as to determine if the probes themselves are actually at fault & that there is a difference in output values.
We know your CHT wiring loom has not changed but the probes have & therefore the termination in it may be different too.
Does the 'new' higher reading probe have a single or multistrand conductor ?
What colour is the connector on it ?
Just trying my best to help here
I know these sorts of issues can be very frustrating & wish that everything was just a simple plug & play scenario, but it is what it is & we have to sort it out.
BTW - what type/model of crimper are you using ?
Jake J
skydancer
RV-7 O-360 CS Prop. Dual Skyviews/AHRS. TruTrak AP
My #4 CHT failed on the last two hours of flight, I repaired it the same way I did to my #4 EGT.
CHT is multistrand conductor, less chance for failure, but still it happened.
The way I did was an experimental, I used molex pin fitted with two pin nylon connector, I also applied solder to the molex pin where I crimped. Then I wraped the nylon connector with heat resistance sleeve to protect from radient heat.
That fixed my #4 EGT issue 100 hours ago (after 3 failures), and I'm hoping the CHT issue will be completely gone after this repair.
Be advised, I'm not giving you any advise of how to fix it, this is strickly experimental for my RV-7.
Apprently the previous rebuild with new spad termininal didn't work for long, that's why I'm trying the new way to result the issue.
Yes, I'm like all of you, sick and tired of repairing the same problem again and again.
CHT is multistrand conductor, less chance for failure, but still it happened.
The way I did was an experimental, I used molex pin fitted with two pin nylon connector, I also applied solder to the molex pin where I crimped. Then I wraped the nylon connector with heat resistance sleeve to protect from radient heat.
That fixed my #4 EGT issue 100 hours ago (after 3 failures), and I'm hoping the CHT issue will be completely gone after this repair.
Be advised, I'm not giving you any advise of how to fix it, this is strickly experimental for my RV-7.
Apprently the previous rebuild with new spad termininal didn't work for long, that's why I'm trying the new way to result the issue.
Yes, I'm like all of you, sick and tired of repairing the same problem again and again.
swatson999
Well-Known Member
- Joined
- Oct 6, 2010
- Messages
- 1,534
Steve
"..it's the relative values/change in readings that matter" -- I'm very aware of this
Bear with me on this, please.
Back on the 2nd Sept you mentioned a probe going to >1600F, I have seen them go to 2500 C which is impossible of course however it was a connector on the probe sidethat caused this high reading.
I mentioned using the calibrated method so as to determine if the probes themselves are actually at fault & that there is a difference in output values.
We know your CHT wiring loom has not changed but the probes have & therefore the termination in it may be different too.
Does the 'new' higher reading probe have a single or multistrand conductor ?
What colour is the connector on it ?
Just trying my best to help here
I know these sorts of issues can be very frustrating & wish that everything was just a simple plug & play scenario, but it is what it is & we have to sort it out.
BTW - what type/model of crimper are you using ?
Jake J
I don't know if the new sensor is solid or multi-stranded...it's *new*, and came with the connectors already on it. I didn't see the need to cut it off and make new ones.
Crimper is one from, IIRC, SteinAir...a ratcheting crimper for red/yellow/blue connectors, but I also at one point used other pairs...all to no avail.
jakej
Well-Known Member
Steve
The single conductor probe wire is a big issue IMO, they are too thin a gauge to just be inserted & crimped, I won't accept them as a good option, I cut the connectors off then double over the wire before fitting a new terminal - that fixes that problem.
The multi strand type is much better however the crimping is critical for good ops in both cases - the Crimper you have is good for that.
Some time ago I mentioned the pink terminals supplied in harness kit - I found that the material is too hard, or it is too thick, which can result in a poor junction. This is evidenced by the extra power required when doing the crimping.
Hope this helps
Jake J
The single conductor probe wire is a big issue IMO, they are too thin a gauge to just be inserted & crimped, I won't accept them as a good option, I cut the connectors off then double over the wire before fitting a new terminal - that fixes that problem.
The multi strand type is much better however the crimping is critical for good ops in both cases - the Crimper you have is good for that.
Some time ago I mentioned the pink terminals supplied in harness kit - I found that the material is too hard, or it is too thick, which can result in a poor junction. This is evidenced by the extra power required when doing the crimping.
Hope this helps
Jake J