1999 astro won't start on cold damp mornings, replaced coil and pick up module, and cap andeverything else, and still no start, the only thing that works is placing a hair dryer near the coil for about a mimute and starts right up.

Your coils arent sealed. The humidity inside the coilsis supposed to be really low so conductivity is maximized.

What do you mean the coil isn't sealed?

replace coil and plug wires. Have had same problem.

just a suggestion but my grandmother had a 90 lumina with the same problem. my dad installed a core heater (similar to the ones used on diesel engines). it was a long time ago and i don't know the logistics of how he did it but i do know that it solved her problem. when there was a rainy spell coming on she would plug it in and had no problems.
not excatly the right way to fix it probably but it worked.