TIT Erroneous Indications, looking for recommendations on the issue

[Mooney_Allegro]

Background:  After overhauling the right turbocharger by Main Turbo, it was time for a flight test after a thorough runup.  During the taxiout, the TIT (only 1 probe on the right turbo) slowly started increasing into the redline and then X'ed out.  I taxied right back to the maintenance facility.   The guys determined that it was most likely a bad TIT probe.   A few days later, they replaced the probe.  I did a runup, and it seemed to be ok.  I departed and ended up diverting about 30 min. after takeoff due to increasing TIT into the red up to 2000'F, despite powering back.   After landing, I didn't see anything unusual with the right turbocharger or anything else for that matter.   In cruise, the MP, RPM, CHT, EGT, oil pressure, oil temperature were all very normal including no unusual burning odor.   In coordination with my mechanic, I departed again, and during the next 3 hours, the TIT showed 40'F, and then during the next hour, slowly increased to 2000'F, before X'ing out.   When it reached 2000'F, I pulled and reset the GEA1 CB (engine instruments), and the TIT started back at 40'F, and would start its slow accent towards 2000'F during the next hour.  It would increase 50'F every 3 minutes.  

I also noticed that when I turned off the alternator in flight, the TIT would drop 75'F immediately, and when I turned the alternator back on, it would increase 75'F.   With the engine shut down on the ground, when I turn off the alternator switch, the TIT drops about 75'F.    

Also, after my 1000 rpm run after the probe was changed out, after engine shutdown, the TIT kept increasing slowly instead of decreasing.

Battery #2 may need to be changed because the volts drop off super fast on the ramp with the engine shutdown.   My plane was sitting in TX for almost a month and the batteries ran down.   They were recharged, but the damage may have been done.   I'm not sure if this had something to do with the TIT errors or not.

I don't think it's a probe issue, because this is a brand new probe and it is acting the same way as the old one with 600 hours. 

I called Garmin today, thinking it could be a GEA1 issue in the tail with the software, but she couldn't help.  She told me I needed to contact a Garmin dealer.    The mechanic suggested that the TIT probe might be getting interference from the alternator lead.  At this point, I don't know what's going on.   

Has anyone else experienced such an anomaly with their TIT Garmin G1000 cockpit indication?

Thx for any feedback.   

[carusoam]

Kinda sounds like a grounding issue may be possible…

Turning off an alternator shouldn’t affect a thermocouple or any sensor…

But, a broken ground wire… may be trying to send errant volts where they don’t belong…

If all EGTs are consistent… the TIT probably can’t get to 2k°F…

The 40°F reading after the reset would be hard to get on something that is at operating temps already…

Check at the hangar over night… all the TCs should be reading nearly the same temperature, without the engine running…  they should be close to the OAT reading…

Be on the lookout for broken or missing ground wires between the engine and the airframe…

Odd that it is only the reading of one TN… after being replaced…

Let’s invite @M20Doc to the conversation… (TIT sensor issue on a M20TN, possible wiring issue)

 

PP thoughts only, not a mechanic…

Best regards,

-a-

[Guest]

First question, is it the correct probe part number?  It would hard to imagine that the TiT would be many hundreds of degrees above EGT.

[Mooney_Allegro]

Hi Doc, it's the correct probe, same manufacturer and PN from the last one.  ALCOR PN: 86309.  

Thanks Carusoam for your insight.

 

[N201MKTurbo]

If the wiring allows, swap the wires between one of your EGTs and the TIT and see if the problem moves or stays the same.

You can test the probes on the ground by taking them out and heating them with a propane torch. You can watch the temperature while watching the color change. it should be similar between the probes.