The glow seems to decrease after driving for about 15 minutes.

I want to suspect some connection that may be subject to thermal expansion, like at the back of the alternator directly under the exhaust manifold, just to make it interesting, but that big connector block where the secondary connects to positive, just off the battery, is all wrapped in tape and therefore suspect, plus there's a crimp-on at the clamp itself.

I suppose I could take five minutes out of my busy day and fix these.

When bad, it apparently affects the spark, and makes the engine stumble.

Thanks. MP