AdamJD

Start here. I haven't had this issue yet, but fly a lot and have hydraulic flaps. So these are a good read for me too.

Patrick - did you find one? I have one off of my F but it has a broken hinge, which is why I bought one from salvage. Wasn't cheap - about $230 - from Dawson Aircraft.

+1 for MooneySpace. Your experience kept me from turning this over to the mechanic who could have possibly convinced me the alternator was bad. They obviously went right to a bad VR without testing it. So thank you for sharing! When I get more time, I'm going to put the tester on both sides of each breaker on the avionics buss and test both sides of the avionics switch. Will report back.

Round 2 of testing. Tested power buss again with engine running, just in case - 13.9 steady. My JPI 830 is powered of the avionics buss. Tested avionics buss with engine running, and it was steady at 13.4, so there's a 1/2 volt drop between those two busses. The JPI fluctuated between 13.3 and 13.5. HOWEVER, throughout this issue, it has read in the low 13s during taxi and runup until after takeoff and then degrades to the mid 12s in flight. Since the battery seems to have a full charge, and the power buss is steady in the high 13s, I'm convinced I don't have an alternator issue and I now have an unnecessarily new voltage regulator. However, to confirm a good alternator, my next step is to test the power buss with the multimeter in cruise flight when the JPI drops to the 12s. If the power buss stays steady in the high 13s, I assume I have either a grounding issue with the avionics buss? Or a bad JPI voltage reading? The whole avionics buss is new as of Nov 22. And the voltage was near 14 steady on my EDM data until about 2.5 months ago, after annual. Thanks for all of the advice!

So if I put the meter on the avionics buss with ALT field on, the meter should match the JPI, right? Seems like an easy check.

Still stumped. On my last flight, JPI reported volts in mid-12s most of the 2.75 hour flight. Event went to 11.8 when I was low power and descending. Took a multimeter out today with a friend. With engine OFF and master / alt field ON, measured ~12.5v at the field connection alternator. Also checked at the VR even though it shouldn't be less than what it was at the field connection at the alternator. My battery was fully charged as well. We then ran the engine and measured at the power buss. It showed ~14v steady on the meter at the power buss, but showed 13.4v. on the JPI. The JPI is powered from the avionics buss. Ran out of daylight to measure voltage with the meter on the avionics buss while the engine was running. I may go out and do that tomorrow. 1) If I have ~12.5 volts on the multimeter at field terminal on alternator with master / alt field ON engine OFF, then field path from battery through everything to the alternator is good, right? 2) If I have ~14 volts steady on the multimeter at power buss with master and engine ON, the alternator and VR are doing their job, right? My JPI was installed in Nov 22 and had shown ~14volts in flight until 2 months ago after my annual. Post annual, it's been fluctuating between 13.5 and 11.8 and trending downward. Last flight was the first time it dipped below 12 on the JPI. Open to any thoughts or ideas.

Great info. I'll report back later this week when I have chance to pull the cowl and start testing. Thanks!

Is there a way to thoroughly troubleshoot without starting the engine? I watched the Mike Busch 'All About Alternators' from 2016. He recommended to measure from field terminal on alternator, to regulator, to switch, and back to circuit breaker with engine off, stating you should see close to battery voltage through that circuit. He stated that if you have 12v at the field terminal on the alternator, then the circuit is not the issue - meaning a bad alternator. I assume that's because in that case ~12v is flowing through that full circuit to the alternator. Did you do that before you tested the alternator with the engine running? Seems like a quick way to determine if it is the alternator, but I'm definitely no expert on electrical systems. I supposed if the alternator is getting ~12v at the field term with engine off, I can do what you suggest (with really long alligator clips) and measure the out terminal from the alternator when the engine is running to confirm its bad. Anything less than 14v (with a new regulator already installed) would mean the alternator is not doing its job, right? Thanks for your advice!

Thank you! That thread is very informative. I'm going to try and dig in and see what I can find. My problem sounds very similar. I haven't yet changed the alternator. But have a new VR, so I'm pretty sure that is good. I'm hopeful this is a connector / wire issue. Will report back.

Bumping up this old thread. I am having the same issue. Voltage has fluctuated between mid 13s and as low as 12.2 yesterday. It has been doing this for a few months now. I had a new regulator put on yesterday and then flew for 2.5 hours. That didn't fix the issue. I've had two separate mechanics look at and clean connectors. See below. Notice that it started in the low 12s for much of the first hour. Then spiked to the low / mid 13s for the second hour (only change was dropping 500' in altitude as I picked up an IFR flight plan). Then dropped suddenly back to low / mid 12s for the rest of the flight. Again, no real event that would have caused that. Note: Before I dropped the plane off for annual in mid-Feb, it was at 14 every flight. The 1st flight after annual in mid-Mar it was between 13.2 and 13.5. It has degraded since to what you see below. There was no direct work to the electrical system during annual. However, they did some extensive work which required dropping the exhaust system. Could moving things around have caused anything? Interested in anyone else's experience or thoughts. Thanks!

Another thread that shows this in action:

Yeah. I watched the IAS swing about 5-10kts - my TAS on the 275 was slowly fluctuating between 135-145kts. I usually see ~143 at that altitude and config. I *think* I can download the flight data from the 275, but haven't tried that yet. But I could see it on both the analog ASI and the 275.

Interesting observation. I had my gfc500 installed in Nov. However, they finished the installation just as the autotrim service alert came out. So I flew it for several months without autotrim. I didn't notice any significant oscillation issues. Autopilot was still enabled, but I had to trim by hand. I recently had the software update completed. I picked up the plane last week and have flown two 2.5+ hour cross country flights since having the autotrim turned on. Now, the plane oscillates slightly in cruise. Both 2.5+ hour flights had +/- 7kt airspeed (and groundspeed) osciallations. BEFORE autotrim was enabled AFTER autotrim was enabled

These worked great for the torpedo lights in my 67F. They dim fine for my needs. Not a large range between dim and bright, but again, they work for my needs. -> https://www.superbrightleds.com/led-light-bulbs-universal-finder/miniature-and-subminiature-bulbs/67-led-light-bulb-12-smd-led-tower-ba15s-base+color-Cool~6500K+packamt-2-Pack I put this in my dome light. Also works well. -> https://www.superbrightleds.com/led-light-bulbs-universal-finder/miniature-and-subminiature-bulbs/67-led-light-bulb-12-smd-led-tower-ba15s-base+color-Natural~4000K+packamt-Single

The elevator must be removed and the paint must be stripped for the inspection. It doesn't say that the weight itself has to be removed. But it's still a pretty labor intensive job for inspecting the weights. "1.3. If the balance weight is determined to be a hybrid weight 430018-1, and initial inspection shows no sign of cracking or chipping, Continue to STEP 2 for further action." "STEP 2 - Detailed Inspection of 430018-1 weights:" "2.0 - REMOVING ELEVATOR WITH 430018-1 WEIGHTS" "2.3. Strip paint from balance weight per applicable Service and Maintenance Manual Section XI" "2.1.0 BALANCE ELEVATOR With 430018- 1 Weights (Complete and Painted)" "STEP 3 - Replacing 430018-1 Hybrid Weights with 430016-7 Lead Balance Weights:" So Step 3 is the actual replacement if the weights are found to be cracked or corroded.

So stupid question from a new Mooney owner. How do we tell if we have the affected counter weights? We can't tell by serial number? My F is at the avionics shop, so I can't just go out and look.

Ugh. Didn't realize we were going to have to wait longer for the fix when driven by the 275s.

It's a shame we can't disable the auto-trim in the AP without disabling the electric trim on the yoke. I'd love to still use the manual electric trim.

Any word on this? I was lucky enough to pick up my GFC 500 install on 11/22, the day after the alert. So I too have my AP, but not the auto trim, as it was disabled in the 275. But my right arm is getting tired...

Received the final verdict. According to the installer, you cannot display more than 1 Misc Field with the GFC500 installed. Must need the space for annunciations. So I will use Tom's workaround. In 3-1 and Basic mode, there certainly is screen space for those small fields. I hope they fix this minor annoyance - after they fix the runaway trim.

That is a great workaround. I'm going to do that too. Thank you!

But you still could keep 2 displayed at the same time? I really want TAS and wind vectors. I can get the other 2 elsewhere. But I can't get 2 to display at one time. Based on your experience, I suspect that maybe the GFC500 annunciations are reserved for the bottom of the 275 and that's why the Misc Fields can't use that space. That's the one difference between his install and mine. I have a GFC500 and he doesn't.

Update - just s Good idea. I'm going to see if he's comfortable going into his sw config settings. I just spoke with Garmin support. They were nice but not overly helpful. They said it's a 'software configuration' and my installer will have to talk with the Field Engineer. I went through the available software configurations when I changed the display to 3-1 to remove heading last night. I could not find an option to increase the number of Misc Fields allowed at a time in the sw config. I've sent an email with screen shots to my installer as well to get his thoughts.

I have that already set to TAS. But I can't find a way to do all 4 at once. See the picture in the original post from my friend's 275. He has all 4 displayed at the same time. I can display either TAS, GS, OAT *OR* Wind Vectors. I changed mine to 3-1 last night and successfully removed the heading ribbon. But I still can ONLY select ONE of the 4 Misc Fields at a time. I really want TAS and Wind Vectors, as I get GS and OAT from other areas (430, iPad, GTX345, etc).

Ok. That helped me with some answers. 1. Per installation manual section 4.2.25.1, you can select from 3 different ADI display modes, one without tapes (Basic), one with just airspeed and altitude tapes (3-In-1) and one with airspeed, altitude and heading (4-In-1). So my friend's config in the photo above is the 3-In-1. 2. Per the pilot's guide, you can only add a Misc Field. However, in the 4-In-1 mode, you can only select TAS as the Misc Field. It doesn't show other options. However, in the 3-In-1 mode, you apparently can add TAS, GS, OAT and wind vectors because the heading tape is gone. So that explains why I didn't see the option for anything but TAS in mine as it was in 4-In-1 mode. 3. For brightness, in the installation manual section 4.2.26, you can select photocell or lighting bus and then configure the photocell. I will report back when I get a chance to configure all of these.