FlyBoyM20J Posted October 14, 2022 Report Posted October 14, 2022 (edited) 1982 M20J, SN 24-1298 My alternator seems to have kicked the bucket. Intermittent lack of charging last couple of flights that corrected itself once, so I was looking for a bad FIELD connection; cleaned that and tightened it; no luck at run-up this morning. Also, should mention: the belt is in great shape. My A&P and I replaced the belt shortly after I bought this plane about 4 years ago. With engine running on ramp: HIGH/LO VOLTS annunciator is flashing, so per the POH, this is a low-voltage situation. Ammeter is discharging and JPI reports 12.5V. Toggling ALT FLD and ALT breakers and MASTER has no effect on the situation. Back in hangar, FIELD wire looks good, VR looks new (is in excellent position above copilot's left knee). I realize I need to measure the FIELD current to be sure, or at least ring out the wire, but based on the findings above, it seems like time for an alternator and I can ring out the FIELD wire when I replace that. I realize this does not rule out the VR but the visual inspection suggests all is well with VR, wires and FIELD all the way to the stud on the back of the alternator. Also, I'm not sure how a failing VR internal circuit would self-correct like a mechanical system would, or like a bad connection would. But I'm not well versed in these systems. Looking at the logbooks, this alternator (and the VR) seem to be original equipment. No mention of them in the logs. Here's the information plate: The Lycoming IPC has PN LW-14333 for alternator ALY-6420LS for IO-360-A3B6D, and Spruce lists the ALY-6520R as the correct replacement for the LW-14333. But there's also an ALY-6520RLS, below that one, at this location: https://www.aircraftspruce.com/catalog/elpages/electrosysalt1.php?clickkey=504227 Does anyone know whether I should get the ALY-6520RLS version or is the information in Spruce correct, and I should order the ALY-6520R? Thanks again, Cliff Edited October 14, 2022 by FlyBoyM20J Quote
bradp Posted October 14, 2022 Report Posted October 14, 2022 Also interested. I’ve got the same question about the -LS suffix. Quote
Guest Posted October 14, 2022 Report Posted October 14, 2022 7 hours ago, FlyBoyM20J said: 1982 M20J, SN 24-1298 My alternator seems to have kicked the bucket. Intermittent lack of charging last couple of flights that corrected itself once, so I was looking for a bad FIELD connection; cleaned that and tightened it; no luck at run-up this morning. Also, should mention: the belt is in great shape. My A&P and I replaced the belt shortly after I bought this plane about 4 years ago. With engine running on ramp: HIGH/LO VOLTS annunciator is flashing, so per the POH, this is a low-voltage situation. Ammeter is discharging and JPI reports 12.5V. Toggling ALT FLD and ALT breakers and MASTER has no effect on the situation. Back in hangar, FIELD wire looks good, VR looks new (is in excellent position above copilot's left knee). I realize I need to measure the FIELD current to be sure, or at least ring out the wire, but based on the findings above, it seems like time for an alternator and I can ring out the FIELD wire when I replace that. I realize this does not rule out the VR but the visual inspection suggests all is well with VR, wires and FIELD all the way to the stud on the back of the alternator. Also, I'm not sure how a failing VR internal circuit would self-correct like a mechanical system would, or like a bad connection would. But I'm not well versed in these systems. Looking at the logbooks, this alternator (and the VR) seem to be original equipment. No mention of them in the logs. Here's the information plate: The Lycoming IPC has PN LW-14333 for alternator ALY-6420LS for IO-360-A3B6D, and Spruce lists the ALY-6520R as the correct replacement for the LW-14333. But there's also an ALY-6520RLS, below that one, at this location: https://www.aircraftspruce.com/catalog/elpages/electrosysalt1.php?clickkey=504227 Does anyone know whether I should get the ALY-6520RLS version or is the information in Spruce correct, and I should order the ALY-6520R? Thanks again, Cliff Have you checked the brushes? Quote
carusoam Posted October 15, 2022 Report Posted October 15, 2022 Brushes wear… when they wear down to nubs… The commutator gets beat up… Then it is OH time for the alternator… Really easy to check status, and replace… Check to see what VR you have while you are in there… If it is the sticks and stones and springs version… your ship deserves better… Zeftronics is a common upgrade path… solid state and works really well… What does your voltmeter tell you? If you haven’t tightened the belt in four years… it may have stretched a bit… don’t be afraid to tighten it using the specs…. Belt slip is kind of odd… it is easy to slip enough to not generate voltage… yet not show any signs of slipping…. Since we are spending your money… that light weight alternator that everyone is using lately…. Gets great reviews for its problem solving chart… PP thoughts only, not a mechanic… Best regards, -a- 1 Quote
OR75 Posted October 15, 2022 Report Posted October 15, 2022 to answer the original question .... the suffix (R or LS or ...) refers to whether the alternator is overhauled (R) etc .... the one you can use are in the Mooney TCDS: Alternators (a) Alternator, 60 amp, Prestolite, ALY8420, ALY8403, AL Y6420 or AL Y8420M (S/N 24-0001 thru 24-2999) (b) Alternator, 70 amp, Prestolite, ALU6421-LS (S/N 24-3000 and on) Quote
cliffy Posted October 15, 2022 Report Posted October 15, 2022 Or any STC;d alternator kit that has an AML for your airplane. There are many. Quote
Beard Posted October 15, 2022 Report Posted October 15, 2022 Not answering your question directly, as it has been answered that the suffix simply means if it has been overhauled, but I would like to offer this. BAS Parts Sales has what you need on eBay. I have dealt with them before and they are reputable and stand behind their items sold and will refund money if it does not work. The one they have for sale is traceable. Some people do not want us install used parts, particularly electronics, but it is always an option in a pinch. You can always phone them and make an offer outside of eBay. I am not sure if you mentioned about getting yours overhauled on your own. Good luck. 1 Quote
philiplane Posted October 15, 2022 Report Posted October 15, 2022 It takes ALE-1013AS brushes. Cost $40, and fifteen minutes to change them with it off the engine, but in many cases you can do it without removing the alternator from the engine. These alternators usually need brushes at the 1000 hour mark. 1 1 Quote
bradp Posted October 15, 2022 Report Posted October 15, 2022 Not to hijack the thread too much but here’s my issue with the field post (excuse my lack of accurate nomenclature for field post as “this guy”). No charge state associated with loose field post. Quote
N201MKTurbo Posted October 15, 2022 Report Posted October 15, 2022 29 minutes ago, bradp said: Not to hijack the thread too much but here’s my issue with the field post (excuse my lack of accurate nomenclature for field post as “this guy”). No charge state associated with loose field post. The post has a rivet formed on the back of the stud that is set over a ring terminal. I have found that if you solder the stud to the ring terminal, it will last forever. You can also reset the rivet. Or you can just buy a new one for $60 or so. I think soldering them makes them better than new. You will have to remove the brush block to do any of these repairs. Just remove the two screws without the wires and it comes right out. Stick a piece of lock wire in the little hole to hold the brushes back to reinstall. Then pull the wire out. 1 Quote
Guest Posted October 16, 2022 Report Posted October 16, 2022 1 hour ago, bradp said: Not to hijack the thread too much but here’s my issue with the field post (excuse my lack of accurate nomenclature for field post as “this guy”). No charge state associated with loose field post. It’s quite common for the studs to come loose in the brush holder. Under the ring terminal is a nut which holds the stud from rotating, this nut often works loose. If you carefully hold the stud from rotating, then loosen and remove the nut and wire terminal, hold the stud again and tighten the second nut to secure the stud, then reinstall the wire, washer, lock washer and nut. Quote
FlyBoyM20J Posted October 18, 2022 Author Report Posted October 18, 2022 All, my apologies, I got sidetracked since I was able to fly that same day once the problem was solved. It was a bad GND connector on the back of the alternator. I am reviewing everything now because this alternator needs replacing soon if not sooner. Here's the connector...doesn't look too bad, but it also looked uniformly "dusty" as if it hadn't been touched in some time. When we loosened the bolt, lots of mineralized dust fell down from between the washers, the lug, etc. We cleaned it and the other end, and that was that. Perfect charging for 2 startups on the ground and then I took off on a longer XC flight (some 6 hours in 2 legs, no issues at all). Cliff 1 Quote
carusoam Posted October 19, 2022 Report Posted October 19, 2022 Great follow up with a pic! Thanks for the details! Best regards, -a- Quote
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