Austintatious Posted October 23, 2019 Report Share Posted October 23, 2019 (edited) Today going into PWA, I started to get a rapid flickering of the Volts high/low Annunciation. It was not the steady flash that you see with a low voltage indication, but a flicker. I pulled the field breaker for the alternator and the flicker was replaced with the steady flash for low voltage. This was about 10-15 min before touchdown. Once on the ground, at 1000 RPM the power fluctuations got so bad that the radios and GNS530w were going haywire. I immediately shut off the avionics switch. Now, rewind a bit. Ever since I purchased this aircraft the ammeter has been bouncy. It is positive but fluctuates. I was told that this was typical. I dont like it though. I can even hear fluctuations in the headset associated with this movement of the ammeter. Today after flying in another Mooney almost exactly like mine I noticed immediately that the Ammeter in it was rock steady in the positive. I cant help but feel that this is how it SHOULD be. Back to PWA.... So I was a bit freaked out that the alternator had failed and my batteries were dead as I was getting the low voltage flash when on batt only. I made a call and got someone to come take a look and help me out as I had 0 means to troubleshoot myself. They were able to help me determine that the batteries were charged AND that they were getting the proper voltage with the engine running. I went to an auto parts store and got some contact cleaner. I removed the master switch from the panel, wires still attached (soldered to it) and disassembled and cleaned that janky little switch real good. This solved the low voltage flash on just battery power, but did NOT solve the jumpy ammeter issue OR the flickering of the low voltage Annunciation. Also, i noticed that the other panel guages were also slightly fluctuating. I do not know what do do next. Does anyone have any idea what is going on ? How can it be normal to have a fluctuating ammeter, but in another Mooney exactly like mine the thing is rock solid at all RPM? I would really appreciate any help on this! I want my ammeter to be rock steady! Edited October 23, 2019 by Austintatious Quote Link to comment Share on other sites More sharing options...
Pritch Posted October 23, 2019 Report Share Posted October 23, 2019 Could be the clutch on you Alternator, mine was doing something similar. Pritch Quote Link to comment Share on other sites More sharing options...
Austintatious Posted October 23, 2019 Author Report Share Posted October 23, 2019 Thanks Pritch. Were your other panel gauges also fluctuating? Do you know of any way to identify if the alternator clutch is the culprit? Quote Link to comment Share on other sites More sharing options...
larryb Posted October 25, 2019 Report Share Posted October 25, 2019 Seems like the field wire is often the problem when you see a wildly fluctuating ammeter. At the alternator it is a small wire with a lot of vibration, easily broken or damaged. In my case it was a bad master switch terminal. Start with a solid visual inspection. Quote Link to comment Share on other sites More sharing options...
carusoam Posted October 25, 2019 Report Share Posted October 25, 2019 The goofy behavior is caused by the voltage at the low end... Alternator sounds, and radio lights blinking are what happens before The final failure... You can read up on alternator things like voltage rectifiers... diodes... burned diodes leave a trace... and have whiny sounds... could be as simple as a loose belt... belt feels tight... doesn’t answer the question... it needs to be tight... Got a JPI? The coolest thing a JPI does for free, without any sensor... records the voltage throughout the flight... want to download some data? When all this is happening... what was your voltage indicating? 11v? what voltage regulator are you using? Zeftronics or the old sticks and stones and springs regulator... AC delco from the 60s? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
jetdriven Posted October 25, 2019 Report Share Posted October 25, 2019 What kind of alternator? I’m getting something Similar. I took the alternator apart and found a burned diode. And when I was putting it back on found the terminal lug loose on the B+ wire, and the wire was burned. So even more fun. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted October 25, 2019 Report Share Posted October 25, 2019 I had a similar problem recently. It turned out to be a loose ring terminal on the brush holder. The back of the field wire stud is peened onto a ring terminal. A few shots with a punch tightened it right up. . Quote Link to comment Share on other sites More sharing options...
jetdriven Posted October 25, 2019 Report Share Posted October 25, 2019 Again what kind of alternator. The plane power and the prestolite Ford are vastly different. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted October 25, 2019 Report Share Posted October 25, 2019 It doesn’t really matter. Although they are quite different in construction, these kind of problems are usually caused by some internal parts vibrating loose. Quote Link to comment Share on other sites More sharing options...
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