What the? Electrical problem

Soooooooooo.

Drive in the garage yesterday from lunch, turn off the car and the radio stays on. Hum. Factory stereo on my '91 MR2.

Basically, the acessory stuff stays on. But, it's weirder than that. The clock lights up with the acessory swithch, so I can watch it and see what's going on. So, I turn off the key, radio stays on, clock stays bright. But the clock gets dimmer and dimmer. Radio finally goes off, then a few seconds later, clock goes dark- BUT - as soon as it does, it immediately gets bright again and the radio comes back on!

So they're getting power that slowly goes away. Once it's all gone, it starts the cycle again! How the heck does that happen? I don't even know what to look for.

Wow... Er... Sounds like you've got an accidental RC Circuit?

There's enough juice in some sort of device acting as a capacitor to run stuff, and something about the circuit is causing it to come back on and juice itself back up below a certain threshold.

Is it a pain to try unplugging the stereo? Does the stereo have both always-on and on-with-acc-or-ignition wiring?

I'm wondering whether its circuitry is fouling up and powering itself and the clock for a little bit, and juicing itself off the always-on once it gets down to a certain point. No, I do not have any sort of explanation, sane or otherwise, for why that would be. It's dumb intuition based on having ancient stereos that would take a few seconds to dim to off over the years...

Unplugging the stereo will be my next step. I have a line level converter on the outputs and an amp in the trunk. I wired that really well, but I assumed that would be the problem even though it doesn't make any sense. I pulled the in line fuse for the amp and it didn't make any difference. So it's something in the facory wiring.

Weird.

Have you added a electric cooling fan to the radiator? Those can turn in to generators as they spin down. BTDT

44Dwarf wrote: Have you added a electric cooling fan to the radiator? Those can turn in to generators as they spin down. BTDT

This just blew my mind. I love you GRM.

No, the fan is stock. And that wouldn't explain it coming back on.

Well, it's acting a little less weird now. Just staying on as if the cylinder is bad or something. But there's no getting past what it was doing yesterday.

Weird.

44Dwarf wrote: Have you added a electric cooling fan to the radiator? Those can turn in to generators as they spin down. BTDT

I learned that the hard way when I was young. I wired in a cooling fan using the positive wire on the coil. The tach started doing weird things and the car didn't want to die when you turned the key off.

Does the car have 'theater dimming' (dome light goes off gradually?). If so, unplug it and see if that straightens things out. If it does, plug it back in and see if there is a diode anywhere in the 'keep alive' circuit and disconnect it. If things quit being goofy, the diode has crapped the bed. BTDT. I once added a alarm system and used the dome light switch wire at the light as the 'trigger' for the alarm system. Immediately weird things happened, for instance the 'key bell' would continue to ding with the keys out and change its tone as the light dimmed and finally went out, the clock did strange things etc. I wound up having to install two diodes: one in the alarm trigger circuit wire and ANOTHER in the right side dome light switch wiring to stop all that foolishness.

In reply to Curmudgeon:

Hum, yes it does have that. That kinda makes sense. Hummm.

I like Curmudgeons answer the best. I think you should call Car Talk. This is Stump the Chump material!

Theater dimming 'timers' are usually (but not always) in the dome light. It would be worth dropping it down to have a look see. The diode might even be up there as well, although I sort of doubt it.

Ooooh. I may have to call Car Talk! It is a good one.

Well, I figured it out. I mean, no idea why it did what it did exactly, but I found the problem. I took the dash apart. Well, I kinda, sorta thought I smelled something but kept telling myself "nah". As soon as I had the dash apart I was sure I could smell something. Then I saw a faint whiff of magic smoke still escaping from the still playing stereo. Ah.

Sure enough, I unplugged the stereo and the clock began to behave normally. I made the mistake of bringing the stereo in the house and now the house smells funny. But I found the problem. Great excuse to order a new Alpine with iPod control and bluetooth. In the mean time, the battery won't be going dead.

Weird one. Thanks for playing.

Take care,

Ed

16vCorey wrote:

44Dwarf wrote: Have you added a electric cooling fan to the radiator? Those can turn in to generators as they spin down. BTDT

I learned that the hard way when I was young. I wired in a cooling fan using the positive wire on the coil. The tach started doing weird things and the car didn't want to die when you turned the key off.

In my 1st dwarf car we were coming around for a re-start when i got bumped from behind, my hand sliped off the shifter and i hit the push pull master switch but the motor continued to run due to the fan but it ran only on two cyl. Made it two laps before i figured it out...

Smokin' stereo, huh? Check for any sort of water stains on the top of the radio. In many cars, the center A/C duct runs over the top of the radio. The radio gets hot, the duct is cold, so in the right humidity conditions you get condensation on the duct. That condensation can drip into the radio. Don't laugh or snort; both Mazda and Chrysler had recalls for that very situation. The fix was to add a piece of aluminum tape to the top vents on the radio so that any dripping water ran off the back of the radio rather than inside it.

44, I bet the other drivers and the race stewards were scratching their heads trying to figure out just what you were up to.