In flight EFIS Failure.

One problem led to another today.

I had high oil temps, and I wanted see if recycling my AF3500 in flight would have any effect on the oil temp readings. I pulled the breaker on the efis, and strangely my oil temp dropped 10 degrees. (putting the breaker back in caused the temps to go back up).

I still wanted to recycle the power on the EFIS, but pulling the breaker and/or turning off the avionics master switch just caused the EFIS to go on battery without the usual "I'm going to shutdown soon" messages that you get on the ground. (Now I see in the manual that auto-shutdown doesn't trigger when there's a/s or rpm, nice.)

I couldn't recall the exact pattern to reset by holding buttons 2+3+4 for 3 seconds. Instead, I was trying to hold down button 1 or button 1+2. Something I did resulted in the unit going into what looks like a continual rebooting sequence. I can't be sure of the exact operation that caused it, but the AF3500 went into a loop and would not come out. It continued on in this state for another hour+ of flight time. It did NOT stop even after landing and shut down. It was still doing the reboot sequence when I left the airport. Eventually the battery will be dead, and I'll see if it comes back to life. Dunno.

I have a video from my phone of this happening if that helps. Is this a known problem? While my actions triggered this, the device seemed to be in a completely unrecoverable state. My panel has suitable backups, so I was fortunate enough to be able to continue the flight to a safe landing.

Thanks,

Don

Don,

What type of system do you have (s or non-s CPU)? Can you tell us your serial number? To turn a unit off after master power has been removed, press and hold button 2, 3, 4, or 5. Button 1 provides a hardware path to apply power to the unit via the battery. Pressing button 1 along with other buttons can cause unpredictable results. Please help us know more about your unit so we can help diagnose the issue and get it resolved for you.


Most likely the cause of the oil temp changing from internal battery and aircraft power is not having a good ground wire to the EFIS case ground screw or a bad engine case ground wire. Do you have a ground wire connected to the case ground screw on the back of the EFIS?

What version of software were you running?

Quote:

---

Originally Posted by Trevor Conroy

Don,

What type of system do you have (s or non-s CPU)? Can you tell us your serial number?

---

I have a non-s system. I'll follow up with SN.

Quote:

---

Originally Posted by Trevor Conroy

To turn a unit off after master power has been removed, press and hold button 2, 3, 4, or 5. Button 1 provides a hardware path to apply power to the unit via the battery. Pressing button 1 along with other buttons can cause unpredictable results. Please help us know more about your unit so we can help diagnose the issue and get it resolved for you.

---

So I did try holding down [5] by itself, and that did not work. I did not try [2+3+4] as per the manual - a case of RTFM on my part. No joke on the "unpredictable" result thing.

I spoke to another AF3500 owner who said he used button [3] to recycle power in flight...

Quote:

---

Originally Posted by Trevor Conroy

Most likely the cause of the oil temp changing from internal battery and aircraft power is not having a good ground wire to the EFIS case ground screw or a bad engine case ground wire. Do you have a ground wire connected to the case ground screw on the back of the EFIS?

---

I don't have a ground wire running to that screw. I'll take care of this immediately. I'm not too hopeful this will make any difference because I have checked for continuity with that screw to ship ground before, and it was fine (grounded through mounting). I'll double-check and install the ground wire regardless.

Quote:

---

Originally Posted by Trevor Conroy

What version of software were you running?

---

The last update file I applied was "AF3000V70104-MV12-AV40", some time back.

Thanks for the reply.

Quote:

---

I don't have a ground wire running to that screw. I'll take care of this immediately. I'm not too hopeful this will make any difference because I have checked for continuity with that screw to ship ground before, and it was fine (grounded through mounting). I'll double-check and install the ground wire regardless.

---

As an aside and benefit to others: This is a HUGE problem with many customers who have fluctuating oil temp/pressure/fuel psi readings. Due to a poor engine ground, the alternator uses our sensor as a ground which causes major problems with sensor readings. Mounting screws are a poor ground and should not be relied on. Just because a multi-meter says there is continuity between the engine and firewall, for example, doesn't mean there is an adequate one. A 26AGW wire would show a low resistance reading on a multi-meter, yet is completely unacceptable for an engine ground (where there should be large braided ground straps from the engine to engine mount and/or firewall).

I "misremembered" about the ground wire. Lesson: don't trust the memory so much when you're over 40. It's installed, and I double-checked continuity. My panel originally came from a panel shop without that ground wire, but I noticed the omission and installed it long ago. Note that I have never had any fluctuating reading issues with fuel, pressure, etc. Only in the past 40-50 hours have I had periodic oil temp issues. I've replaced the probe and more recently the vernatherm. So it was with a new probe and new vernatherm that I noticed that pulling the breaker on the AF3500 causes a magically instant 20 degree immediate change in oil temp.

Unfortunately, I guess I'm back to the drawing board on trouble-shooting oil temp.
At least I can avoid the funky reboot failure, though you guys should eventually try to fix that.

What happens to oil pressure when you turn off the Alt Field switch mid-flight?

Oil temperature, not pressure. The Oil temp goes to a normal reading when I disable the ALT. Again, on many flights, the oil temp just stays on 187. The other day it was reading 230, with all other cht/egt temperatures normal to low. I disabled ALT, and the temps dropped to 180.

Excellent, that isolates the problem. Your alternator is using our sensor as a ground path through your engine to the electrical system. You will need to install a large gauge wire from your engine to the mount and firewall and ground bus to ensure your alternator has a low resistance path (that can handle 60 amps of current).

Trevor,
That wire should be able to handle the current that the starter motor draws. That would be quite a bit more than the alternator puts out.

That is a great point!

I started this post with 2 problems: the reboot loop on the efis, and the oil temp issue.

Since all of the discussion is now on the oil temp probe, I started a fresh thread with a more appropriate label for that topic. As for the inflight reboot loop, I'd be curious if there's ever a fix for this, but it's not a problem since it is easily avoidable.

Trevor,

I responded to the oil temp post a few lines above this one. I ended up having to ground my oil filter adapter to get rid of the fluctuating oil temp. That was with a heavy braid between the case and the engine mount. It seems like the oil filter adapter isn't necessarily very well grounded. Makes sense if you consider the gasket and a possible paint under the mounting hardware.

Dave

Dave, that is something I did not consider. Thank you for the info. There is also a 3M gasket between the 90deg filter adapter and the engine that would act as an excellent insulator.

The oil filter adapter is bolted to the engine. It's grounded, period. This thread is chasing ghosts.

dhall_polo, does your oil temp sensor screw into the oil filter adapter? Do you have a #10 or #8 ground wire from the filter adapter to the engine case? If you turn your ALT FIELD off and the Oil Temp changes, a grounding issue must be the problem. If you've exhausted all possibilities, we do have 2 wire oil temp sensors that we can order. We've found only a few situations where they were needed after all attempts were made to properly ground the alternator and engine to the airframe.

My oil temp probe is in the usual spot on the oil filter adapter. The oil filter adapter is grounded via the bolts that attach it to the case, so the gasket is irrelevant. Despite that fact, I added a ground wire to the temp probe itself, and this made no difference. There is still some in-flight condition that can cause the oil temp reading to rise, and turning off ALT1 still results in an immediate drop to the normal or expected oil temp value. At this point, I've double and triple checked engine ground and AF3500 ground, and I've added the probe ground as an extra measure even though it already checks out as grounded with multimeter.

Which 2-wire oil temp probe should I order for Lyco IO360?

The two-wire sensor is a UMA p/n 1B3 and the price is $75. You can give Tricia a call to order one.