Can alternator problems be intermittent?

Last question about this before I bite the bullet and pay several hundred dollar to get it fixed. I thought that an alternator either worked or it didn't. I have a 2004 ford escape and although my battery light stays on most of the time, it gets me from a to b without issue 99 percent of the time. Twice in 2 weeks, though, my alternator stopped charging and I broke down. I've tested multiple times and the alternator was charging, but both times I broke down it wasn't charging and I was running off battery only. Does this sound like normal behavior or does it sound more like a bad connection somewhere? The connection to the battery is clean and tight, but the alternator is so hard to get to that I can't really tell if all else is good.

Yes. My alternator took turns in charging and then not. It's unlikely to be a bad connection as the alternator doesn't move or vibrate. It's 15 years old so it has done well up to now.

Take it to an auto parts store. They will test it for free.

The auto parts stores can test everything. And it could be something like a battery cable or cable end.

Do take the time to see if all else is good. Connections at both ends, quality of the wire along the way, good ground. And, how about the alternator belt?

Any time the battery light is on, the alternator is _not_ working properly.

From what you describe the rectifiers in the alternator are failing, or the connections to them are corroded or damaged somehow.

The warning light connects between the switched ignition power circuit and the feed in to the alternator field regulator.

As soon as the engine starts, the alternator should produce its own internal auxiliary supply to feed the regulator, rather than drawing any current through the warning lamp.
If the lamp stays on, that is not happening.

Sounds like the brushes in the alternator are worn out

Before you start swapping out parts that are still good, check the charging system fuse.

My alternator went bad in a Subie I owned, and it was intermittent like that, even charging at some RPMs and not others. I found out there was a recall on it.

Yes, certainly. Anything electrical/electronic can be intermittent, a common failure mode. Internal solder joints can crystallize and screw w connections can loosen from vibration. Best you take it to the 'Zone and strike it with a rubber mallet in several places while running. This will show any intermittents.

If you want to tackle it yourself, take it apart carefully, push on solder joints, try screws at connections. Might possibly be a field fuse or fusible link external to the alternator. (Fords do have an ext. Field fuse. So do a lotta Jap N/D units.)

My N/D alt. To my Toy had low output. Turned out there's a heat sink to regulator that required silicone heat sink compound; it had dried from age and pulled away. When reg. Got warm, output dropped. When starting from cold, it was ok for a while.

Tow bills cost more then replacing the alternator. When that red warning light that means the battery isn't being charged comes on you're lucky if you have 15 minutes driving time with the headlights off.