201er Posted January 6, 2012 Report Posted January 6, 2012 Last time I flew, I was cruising along when all of a sudden the low voltage light comes on. I then looked at my ammetter and it was way negative indicating a discharge. I was daytime IFR in VMC and was already thinking through my plan of cancelling IFR, shutting down unnecessary electrics, and where to land. I did not touch anything and while I was thinking, the voltage light turned off, ammeter normalized, and electrics ran fine the remainder of the flight and the next two. Anyone ever experience something like this? Any rational explanation? Is this any kind of indication of imminent alternator trouble or just some strange isolated occurance? Quote
jetdriven Posted January 6, 2012 Report Posted January 6, 2012 Ours has done that 3 times. Once the field wire terminal broke at the alternator. A few days later the output post on the alternator melted off, turns out our superstar former mechanic never tightened the nut on either post. It just happened again, this time the #1 lower wrap baffle broke and the all thread rod got loose and chafed the field wire. Have a look. Quote
garytex Posted January 7, 2012 Report Posted January 7, 2012 Also check connections on master switch, especially if they are spade connections. They evidently can get a little corrosion and the field will be intermittant. Quote
mooney2201 Posted January 9, 2012 Report Posted January 9, 2012 i would look at all connections at the alternator, alot of vibration,,may be corroded field terminal... Quote
201er Posted January 15, 2012 Author Report Posted January 15, 2012 Alternator hiccup turned into alternator nightmare. This morning I fired up the engine to be welcomed by low voltage alarms immediately and discharge on the ammeter. I had just preheated the engine and the morning was absolutely frigid (sub 20F with massive wind chill) so I decided to run the engine a little longer to warm it before shutting. Flipping master on/off, pulling alt field circuit breaker, turning extra things off, none of this helped. I shut down engine after it was warm enough for a hot start and got out to check the alternator belt. Gave it a tug back and forth and seemed fine. Got back in, easy hot start, alternator working off the bat! I took my time taxiing out, did my run up. Voltage still good. At the final stage of runup where I bring the power back, the alternator did not come back in when I reapplied power back to 1000RPM. Once again no amount of fiddling would bring it back so I taxiied back and shut down. Some suspicion rests with the voltage regulator. But one question I have is, can the cold be doing something to mess with the alternator? My guess is if there's enough power to turn the starter, there's gotta be enough for the alternator field right? I'm worried to start it again (unless I'm ready to fly it directly to my mechanic) just to test it. Quote
jetdriven Posted January 15, 2012 Report Posted January 15, 2012 Check the output terminal on the alternator, the ring terminal for the filed wire, and the wiring to both. I bet your problem is in there. It is free for you to look. For a mechanic, thats 200$ Quote
201er Posted January 15, 2012 Author Report Posted January 15, 2012 ^Could you please explain to me (perhaps photos/diagrams if available) where and what I'm looking for. I admit my airplane maintenance apptitude is about on the level of a chipmunk repairing a beaver dam but I'm trying to learn. Thanks! Quote
201er Posted January 15, 2012 Author Report Posted January 15, 2012 Which way are you looking? Top down or bottom up? Do you take just top cowling off or gotta take em both off? Quote
jetdriven Posted January 15, 2012 Report Posted January 15, 2012 that photo is the entire cowling off, sitting on the RH side of the engine looking up and aft from below. Those two cylinders you are looking at are #1 on the right and #3 on the left. The big shiny thing is the alternator . Ours had 30 hours on it before the post melted off. We only paid 1000$ to have him install it. Stupid me. I should have paid him 2500$ to do it right. Quote
201er Posted January 19, 2012 Author Report Posted January 19, 2012 Ok, flew to my mechanic today with alternator inop. I started up on remaining battery alright, turned off a lot of stuff (radios, audio stuff, electric gyro instruments) took off, saw a glimpse of alternator voltage so I got optimistic that it was working at full power. So I decided to retract the gear using alternator power but sure enough as I trough the switch up, the alternator went back out! Too late to change anything but at first I was concerned the gear wasn't fully raised. The red light was out on the panel so I decided it must be. I flew the whole way with pretty much only the transponder running. Put the gear and flaps down on remaining power no problem. Mechanic worked his magic and said it's not the alternator (nor a loose connection) but the voltage regulator. He didn't have one in stock but I need the plane for a trip tomorrow. So we located a part at Robinsville so I rented a cherokee from them and flew to get it. My goodness, cruising at what is normally my pattern speed! Anyway, got the new regulator and all seems to be working ok. A good deal cheaper to fix than replacing alternator! Quote
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