Figured I would share this for giggles and for anyone curious about alternator rebuilding. Last summer my high output alternator roasted a bearing so I swapped it out with an OEM that I had kept in storage for many years to use as a backup. Well I suspect the sub zero temps we had a couple weekends ago for several days put enough of a drain on my battery (an AGM from Interstate) to overstress the rectifier in the OEM unit, so I had to take a day and do the rebuild on the high output to get it back in (why hadn't I done it sooner? Juggling way too much and kept procrastinating). So a few days ago I fired up the pellet stove in the shop, threw some DIO on the stereo and went to work.
The victim. This was originally sold as a Beck/Arnley unit that I had gotten back in 2007 or 2008. IIRC that original unit ultimately had either the windings or the rotor go out so I had to replace the whole unit. Took some time but a reputable auto electric shop sourced another 120A unit that when I received it, was identical to the original B/A I had previously.
Close up shot of the info tag. When you research the part number now you find some weird NAPA alternator that's only advertised as an 80A unit, so my impression is that the only high output option anymore is shelling out big bucks for a Mean Green unit, which I've heard mixed reviews of. Honestly I'd love to get a dead one and investigate exactly what failed on it. Also notice how in the upper right corner it says "12V 80A PASS". I remember asking about this when I picked it up and was told that's because the vehicle it's designed for (ie: the US spec FJ62) comes factory with an 80A unit, so the pass/fail is just based on it meeting (in this case exceeding) that spec. Notice the actual current it tested at when at 6000 RPM....
Now before the bearing went out I hadn't noticed any electrical issues beyond the typical voltage drop when at idle with a moderate current load. But when I pulled the rectifier I saw two diodes had at some point blown out:
This is the bearing that had failed. The tail bearing, which holds very little lateral force, unlike the nose bearing which had to take most of the force of the belt tension. Erego the tail bearing is often much smaller than the nose bearing. When I turned it by hand I could feel just how "gritty" it felt and how much it was grinding and eating itself alive.
The victim. This was originally sold as a Beck/Arnley unit that I had gotten back in 2007 or 2008. IIRC that original unit ultimately had either the windings or the rotor go out so I had to replace the whole unit. Took some time but a reputable auto electric shop sourced another 120A unit that when I received it, was identical to the original B/A I had previously.
Close up shot of the info tag. When you research the part number now you find some weird NAPA alternator that's only advertised as an 80A unit, so my impression is that the only high output option anymore is shelling out big bucks for a Mean Green unit, which I've heard mixed reviews of. Honestly I'd love to get a dead one and investigate exactly what failed on it. Also notice how in the upper right corner it says "12V 80A PASS". I remember asking about this when I picked it up and was told that's because the vehicle it's designed for (ie: the US spec FJ62) comes factory with an 80A unit, so the pass/fail is just based on it meeting (in this case exceeding) that spec. Notice the actual current it tested at when at 6000 RPM....
Now before the bearing went out I hadn't noticed any electrical issues beyond the typical voltage drop when at idle with a moderate current load. But when I pulled the rectifier I saw two diodes had at some point blown out:
This is the bearing that had failed. The tail bearing, which holds very little lateral force, unlike the nose bearing which had to take most of the force of the belt tension. Erego the tail bearing is often much smaller than the nose bearing. When I turned it by hand I could feel just how "gritty" it felt and how much it was grinding and eating itself alive.