Main battery charging weirdness, classic Prius
Any advice or suggestions will be greatly appreciated. I think if I don't clear this up soon, my '01 Prius will destroy my battery - it's already overheated it once from over-charging (see below) - after 140,000 miles, it has the original battery (and the original brake pads!) and I'd hate to lose it now.
There are lots of weird symptoms, and a dealer has already failed to diagnose the problem, so please pardon a lengthy post because I don't know what might be a clue...
For the past few days, my car has been sometimes failing to charge the battery when it should, and sometimes over-charging it.
I spent the past 20 days in Seattle, arriving in icy conditions where I had to use chains on black ice and rutted ice: lots of shaking and jarring. Next morning, the car started, ran rough for 10 seconds, and shut down with lots of warning lights. This seemed similar to the P3191/P3192 start-then-die problem, which I've also had (in very warm weather, not very cold) and never gotten fixed... but this time, it didn't start up on the second, or third, or fourth try.
Two days later... I'm about to get it towed to the dealer... I keep trying to start it, and on the third try, it starts! The "Check engine" light was on solid, not blinking, so I drove it 1.5 miles to the dealer. I noticed on the way that the regenerative braking didn't seem to be working - no subtle whine when I stepped on the brake gently.
The dealer "diagnosed" carbon in the throttle body, and wanted $250 to clean it, and told me it was driveable. So I drove the car away - it was running OK - and figured I'd have my mechanic look at it when I got home (CA Bay Area - moderate temperatures), and risk cleaning the throttle body myself if it acted up again.
One weird thing: When I first saw the car again at the dealer, when they drove it out to be picked up, the main battery was on 1 bar. They said this is normal - though I'd never seen it before - confirming my distrust of that dealership. I later found out why: When driving at very low speeds, less than 8-10 MPH, the battery would not be charged. So if I was in a long line of traffic at a traffic light, or on a freeway in bad rush hour traffic, or driving around a big parking lot, the main battery level would go down and down and down, all the way to 1 bar... while the trip-info display showed the car sucking juice out, but never putting it back. At higher speeds (even normal city street driving), it would charge just fine. Putting it on "defrost" so the A/C was on also seemed to charge it at low speeds, but I'm not sure of that.
OK, so avoid rush hour and try to limp home to a mechanic I trust...
I didn't drive it much in Seattle, but I did a little... the car engine quit on me once in the middle of the road (more warning lights - restarted fine), which it's never done before.
I noticed that sometimes the battery would be full (to the top, not the normal 3/4 full) after decelerating off a freeway, something I've never seen before.
On the long drive back to the Bay Area yesterday, the cruise control didn't work... then the red triangle cleared itself (the way it does a day or two after a P3191/2 error), and the CC started working. The Check Engine light stayed on and is still on - not normal behavior for my P3191/2 problem.
Tonight, I noticed that the battery was full after driving up a hill to my girlfriend's house. When I left a few hours later, I noticed that (according to the trip info display) the car was continuing to put juice into the battery even though it was full... the engine kept changing speeds, sounding like it was putting itself in gear and working, even when the car was slowing or stopped (so it really was doing something effortful, probably charging the battery)... and the yellow turtle light was on, though it felt like it had normal power e.g. starting from a stop sign... and the battery cooling fan came on loudly. So I stopped the car, turned it off, turned it back on, and the car stopped trying to overcharge the battery (which quickly went to the normal 3/4 full), and behaved normally for long enough to get it home.
I did notice, once, several months ago, in very very slow freeway traffic in the Bay Area, that the main battery was down to 1 bar and the car was sluggish. So the symptom of the battery not charging at low speeds isn't entirely new. Perhaps it's just different driving conditions in Seattle that made me notice it more... but I don't fully believe that, because it would go down to 2 bars just from normal driving (e.g. parallel parking) and I don't believe it used to do that.
So - is the battery charging problem independent of the engine problem? They sure seem related... but there's no obvious connection...
I'm trying to decide whether to take my car in first to an excellent mechanic (but who's not a dealer) or to the local dealer (who I have not much experience with - Toyota of Palo Alto).
Many thanks to anyone who's read this far!