EGT Moritz gage flaky, always <600F

[THill182]

Question on how best to troubleshoot: About 4 hours out of my last annual, on a cross-country, the Moritz EGT gage started to fluctuate wildly (was running LOP at the time), and then eventually settled at the bottom (around 500F as I recall). The EDM was stable and the Engine ran just fine. When I start the plane up when it's cold, the EGT starts showing the increase in EGT, but now stops at the low end/display at/around 500F.I

It hasn't been essential for operations since I have an EDM700 that displays everything I need to know. Still, of course I want to fix that.

My mechanic told me that there is nothing obviously missing or loose anywhere near the sensor. 

How best to troubleshoot this, without starting to replace parts to see what works. Is there a procedure to test the sensor, or the Moritz gage (which, if it is broken, not sure if/how to repair that...).

 

Anyone know? 

PS: 2000 Ovation II, with 310 HP conversion.

 

 

[M20S Driver]

Is it possible that the EGT probe is going dead?  

My EGT on cylinder #3 was behaving the same way and a new probe solved the problem. 

[LANCECASPER]

Read the 3rd and 4th posts down in this thread:

 

[Mark89114]

Well mine just started reading on the high side by several hundred degrees....mayne we can combine the 2 and get an average?  Sarcasm font.  Going to replace with JPI most likely.

[Godfather]

Don't waste your money and time. The manifold and egt are the two most common failure points on these units. Cheapest way is to inop the broken portions and buy certified replacements. Otherwise a jpi 900/930 or ei 50 is the way to go. 

[carusoam]

Moritz is always going to get some heat, because they went out of the business of supporting their instruments...

But before we throw the baby out with the bath water, know that the EGT sensor is in one of the most harsh environments...

First thing a PP would want to do...

1) identify where the EGT sensor is that services the ship's EGT gauge.  The O has a separate thermocouple on one side of the engine after three exhaust streams come together... this is why the ship's gauge usually reads higher than the other six.  Three exhaust pulses in the same time the others see one.  All of them have an averaging function...

1a) The ship's EGT is a bit down stream from the exhaust valve (hottest point), but the three exhaust pulses still make it read higher than the individual EGTs closer to the valve. (My ship's EGT is analog and My comparison may be out to lunch... I haven't looked so close in several years...)

2) See if the sensor has been eroded.  The thin wall TC has a tendency to get beat up.

3) check all the wiring and connections back to the instrument.

4) It may be easier to test everything with a different TC.

5) or test the TC with a different meter....

6) or put the EGT sensor in ice water, followed by boiling water and see if it behaves properly

7) The second important use of the Ship's EGT is the mixture setting during the climb.  In the O1 the EGT has a blue box on the instrument.  Keep the mixture in the blue box.  The newer Os have a white box on the G1000.  You definitely would prefer using the ship's gauge for this.  You could use a single EGT and use the blue/white box technique...  when staying 200° - 300°F ROP it won't make much of a difference which one you actually use.

8) T, did your mechanic pull the ship's EGT TC from it's mount to see if it was healthy? (Was he looking in the right place for it?)

Private pilot thoughts only, not an instrument guy...

Best regards,

-a-

[Tommy]

Following this, mine has also done! Not that I use it at all now with EDM but nice to have some redundancy. Is this the replacement probe for '81 J? 

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

ALCOR BY TEMPEST EGT / TIT TYPE K THERMOCOUPLE CLAMP 3-3/8 MAX

Alcor P/N: 86255

 

 

[THill182]

Thanks for feedback. My panel is pretty much original at this point, and frankly I like it (very used to it, know what it is like when individual components fail, etc.) Generally have toyed with idea to go electric but never quite saw an urgent need. 

I'll replace the sensor and have an avionics shop look over connections once more. If it is the Moritz gage and either way, will start planning for some downtime to refurbish a few items (fuel system overhaul and magneto service is coming up anyway). 

Right now I have a JPI EDM 700 and a Shadin fuel flow, and another RPM gage after the 310HP (2700 RPM) upgrade. So most of the Moritz functionality is already displayed somewhere else. Is there a cheap/easy way to put oil temps, ambient temps, and maybe something else useful into the same (rectangular) space? I hate to recut the panel, and then put in old steam gages; but the alternative is the 40k redo, followed by training costs/time to re-familiarize myself with a new panel and gages, and the pucker factor when things fail that I have never seen before.

Hopefully, it's just the sensor....

 

 

 

[carusoam]

Probably just the sensor...

Looking forwards...

The JPI 900 may be a good addition. 

• Relatively small ish, but very readable...
• Approved for primary instruments, making a good replacement for things that fail along the way...
• When combined with CIES Fuel floats, more accurate than the original equipment for fuel level.

You will want to see if it fits where the O1’s MP, RPM, EGT gauges went... The O3 may have some empty space there already?

Doesn't the O3 have the G1000 with all this engine monitor already?  The white box and all?

Fuzzy memories of a PP, not an instrument guru...

You can always go old school... (no power required, works off the voltage differential generated by the thermocouple)

http://www.aircraftspruce.com/menus/in/egtchtinstruments_alcor.html

It was the EGT gauge of choice in early Mooneys... 

Best regards,

-a-

[Godfather]

29 minutes ago, carusoam said:

Probably just the sensor...

Looking forwards...

The JPI 900 may be a good addition. 

• Relatively small ish, but very readable...
• Approved for primary instruments, making a good replacement for things that fail along the way...
• When combined with CIES Fuel floats, more accurate than the original equipment for fuel level.

You will want to see if it fits where the O1’s MP, RPM, EGT gauges went... The O3 may have some empty space there already?

Doesn't the O3 have the G1000 with all this engine monitor already?  The white box and all?

Fuzzy memories of a PP, not an instrument guru...

You can always go old school... (no power required, works off the voltage differential generated by the thermocouple)

http://www.aircraftspruce.com/menus/in/egtchtinstruments_alcor.html

It was the EGT gauge of choice in early Mooneys... 

Best regards,

-a-

I hope it is just the sensor. If so it will be a very easy fix.  If not don't try to chase down the problem. 

'Your current fuel sensors (2 per tank) are very accurate and you will not need the CIES sensors. 

The guages were in a great spot but almost impossible to find something that can fill the space. 

So yes @THill182 I agree that it is a very slippery slope and you can drop 40k very quickly before it's done. 

This is why you see a lot of forsale planes of this vintage with black tape on two or more guages (not something I'd recommend but it's your plane)

Is it legal to have the old tach showing past redline even with a digital readout?

 

edit:

I absolutely enjoyed using the moritz guages for the past 15 years and tried my best to keep them going. However, every Mooney shop I talked to including Don said to move on when things go astray.  So I did and now I'm getting everything ready for that 40k upgrade

Edited July 22, 2017 by Godfather

[THill182]

Thanks again. By the way: Mine is a 2000 O2, upgraded to O3 (310HP). The original RPM gage is technically INOP and part of the 310HP conversion is the extra legal RPM gauge. Still, the old one shows the numbers correctly (even though max RPM now is >2,500 RPM). 

I hate the power of consensus when it means major cost and downtime -- but after reading all the other posts and thread on Moritz gauges, and given that even Don says "let it go" when the time comes -- I'll just hope it's the sensor for now and start planning for a major upgrade...

PS: Maybe it is just that I am older now: But it seems to me that the stuff that was in the panel when I learned to fly 30 years ago was timeless: No electronics that became obsolete. In particular with engine gauging, why do I need fancy displays (not that the Moritz was particularly "fancy"). Anyway, no better way to turn discretionary income into noise than owning an airplane....

 

[carusoam]

I had the original rpm gauge updated to show the proper 2700rpm red line... close eyes when the bill arrives...

I had some idea of keeping the panel looking original while functioning properly...

So many improvements come with the updated stuff.  The modern tach does the math during the run-up...

The JPI or EI have so many functions including alarms...

I'm considering adding a JPI 930. It will probably occupy a spot in front of the copilot. Where the JPI 70X currently resides...

When the 40AMU upgrade hits, the 930 will get relocated...

More PP ideas...

Best regards,

-a-

[PMcClure]

Mine doing exactly the same thing. Found the sensor was faulty. 

 

[THill182]

To close the loop: It was the sensor. Replaced sensor and readings are normal again on the Moritz gauge. So no major panel redo required this time... Phew...

 

 

[carusoam]

Great follow,  TH!

Best regards,

-a-

[Tommy]

On 04/08/2017 at 10:40 AM, THill182 said:

To close the loop: It was the sensor. Replaced sensor and readings are normal again on the Moritz gauge. So no major panel redo required this time... Phew...

 

 

Great news. do you have the part no. of the sensor?

 

thanks 

[THill182]

Preferred part number according to parts manual (2000 M20R) is 86255, and at Aircraft Spruce is available here: http://www.aircraftspruce.com/catalog/inpages/alcor_probes.php