Percolation? Heat soak? Don't drive during summer??

DentalDart said

It was like that before I took it apart and it never caused a problem... that I know of.

Click to expand...

Strange. I thought it was a new symptom after it was back in..
I keep misremembering things from your other threads!

It's still not normal and may be causing other parts to go bad or it's caused by something else already being bad that gets worse with heat..

I'd see if bypassing (temporarily) the ballast changes it, or confirm the tach is the cause. A good tach shouldn't cause that..