[Amc-list] a study in failure

[Tom Jennings <tomj@xxxxxxx>]

The generator died on Wednesday. It died because I chaned the radiator and 
fan. It really is a case study in failure modes and how they happen.

Driving back from Irvine Wed night, about 5 mi from home I started getting 
fan belt slippage when I revved more than 2400, and headlight and dash 
brightness changes that always means charging problems. Nothing serious, 
though it did alarm me a bit. Made it home just fine. Popped the hood, 
poked the fan belt and it was much looser than I'd left it a week ago. At 
idle, there's a fan-belt-y scritching sound, like a wet or loose belt... 
when I revved it from under the hood, the headlights visibly went 
bright/dark/bright/dark, the variable output of a flakey charging system.

Next morning I start the car to examine, noise is still there. Moving 
around the car (so ear directionality works) I decided it was the 
generator; when I put my hand on it I could feel it vibrating. Bad bearings 
would be no surprise.

I pull the generator, and here's the cascade of related failures:

Both armature (A) and field (F) wires are very loose. The gennie has been 
charging just fine anyways, but the connections were loose and greasy, 
waiting to fail. The ground wire is tight, but missing one ear of the spade 
lug.

Pull out the mount bolts, the front lower mount/pivot falls out. An old 
fracture, it's all rusty. This is most of the noise source; the front of 
the gen dropped, loosened the belt, and was jumping up and down as it spun.

Spun by hand, the front bearing is noisy, the rear bushing quiet, but the 
oil cup long since busted off so it's gone un-lubed for who knows how long.

The brushes wore a deep, deep groove in the commutators, the damned thing's 
probably original. It charged just fine though! A testament to generator 
reliability.

So putting on the new fan belt and tightening it popped the broken bolt out 
of place -- after 200 miles of driving -- causing belt slippage and 
vibration, which wiggled the loose wires and made the charging system 
intermittent.

Chuy's Electric in East LA had one in stock! $60, lucky me. Repaired the 
ground wire, broken bolt, etc it all went in OK.

Man, generators suck for making juice. Does basically nothing at idle, 
charges somewhat OK at 1800 rpm. They weigh 3X an alternator, but 
alternators are not Cool.



(I worked with this guy, Owen, who bought only old Cadillacs (late 1970's), 
did zero maintenance and drove them til they died. "I don't open the hood, 
it only costs me money". There's something to this, you change a fan belt, 
who knows what else will break! :-)
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