hello all, I am having a strange electrical problem on my 2000 ex (d16y8)

I notice it mainly at night with my headlights on, but I recently verified that it occurs with the headlights off as well, it's just easier to see with them on in the dark

the problem is this: from time to time I will notice a periodic dimming in the intensity of the headlights. They will get dim for maybe 1/2 second then return to normal brightness. This might persist for 5-10 minutes. While the problem persists the dim spells sometimes get dimmer and dimmer, and occasionally the SRS light illuminates. All the while the engine seems to keep running just fine with no loss of power. When the lights return to normal intensity the SRS light goes out

I have had the alternator and battery tested and both tested good. This leaves (as far as I can tell) a corroded ground somewhere as the likely cause. does that seem reasonable? can anyone recommend any good grounds to check? maybe some that are subject to the effects of some good old ohio road salt?

I welcome any other advice or suggestions also! thanks!