My Lexus ES250 has been telling me it's ready for retirement. I wish the price tags on the new cars weren't giving me a different message.
The new problem is this: while driving if I apply an electrical load the voltage drops briefly (but very deeply) then recovers. Pressing the brakes causes the headlights to blink briefly but noticeably, and the radio goes off for a heartbeat. Pressing the high fan speed actually caused the engine to stop for a moment.
It's a transient effect. Even with the brakes held or the fan left on, everything seems normal after a moment.
Someone has said the main power lead at the battery has a bad connection. The alternator is supplying the load, and when something is switched on it can't adjust to the new load quickly enough without the battery.
I hope it's that easy, but it doesn't quite add up. (And it seems to be intermittent, so I'd like to fix the problem "for sure" in my garage rather than find out I guessed wrong in the middle of an intersection somewhere.)
I don't like the theory because if it were the problem it should show up with the engine not running. If the connection between the battery and the main power buss was bad, without the alternator running lights would be dim, etc.
I've found postings from a handful of others with what seems exactly like my symptoms. The describe fruitless trips to the dealer or their electrical shop, multiple replacements of alternators and batteries, and no solution.
So I'll check the connection 'cause it's an easy fix, but I'd be grateful for a couple of "seconds" on that as the answer.