Car electrical question

Another question about my car!

1996 Toyota Tercel.

Had a problem earlier this week with the stereo - the display would stay on, even when the car was off, so I took it out, unplugged it, plugged it back in and it fixed it for a day or two before it happened again. (no audio at all or response to button presses during the malfunctioning times)

Then I left my headlights on overnight, jumped it and went on with my day, but have realized that I don’t have a chime anymore when I leave the headlights on :eek:

(Yes, I walked to work today, why do you ask?)

Are these two issues related, and if so, how do I fix them? Fuses seem like the obvious answer, but not only do I not know where they are on this car (yes, I’ll google it if need be), but it seems like things getting stuck on doesn’t indicate how fuses work.

Any help is appreciated!

I’m guessing they’re unrelated, unless the stereo’s display was subliminally telling you to leave the lights on.

As for the stereo - sounds like it’s got a problem internally that’s causing it to leave the display on and otherwise play dead, and the power cycling cleared the fault temporarily. The fix will probably wind up being to replace the head unit.

Oh, ok. That part’s fine, I was actually planning on replacing it soonish anyway, I suppose now it’s just a slightly higher priority.

Any idea on the buzzer though? If it’s not a simple fix, my roommate is electrically inclined, and we could probably rig something up, but I’m sure it wouldn’t be as elegant.

Chimes and other features can usually be programed if you have the instructions from the owners manual. The programing of these features involves pushing the buttons in a certain order on things you might think are unrelated to the issue.

With my car, a Pontiac, to enter programming mode I turn the ignition to run, to disconnect the alarm system. Turn the ignition to off. Remove the radio fuse. Turn the ingition to accessory. Count the number of chimes I hear. The number of chimes will tell me which features are enabled when I consult the chart in the book. There are 4 mode settings, the car comes set to mode 4.

There are a whole list of steps to set and customize my settings from this point. Once I am in programming mode, to change the mode I turn the courtesy lamps (that’s right, the interior lights) all the way up, listen to the chimes to find what mode I am in, turn the courtesy lamps off and it will switch to the next mode.

Sounds screwy but that is how it is done.

You may have lost these settings when you unplugged the stereo. Find an owners manual or ask a dealer, or find a Toyota forum on line and ask them. There is probably nothing broken you just need to recover the settings.

You could have two separate problems, or they could be related.

I don’t know how your Toyota is wired (maybe one of our resident car experts can comment on that) but on most cars there’s a relay that gets turned on by the ignition switch. When you turn the car off, the relay turns off and cuts power to things like the radio so that they can’t kill the battery. The radio should have a second electrical connection to the battery that bypasses this relay so that it keeps its settings. Sometimes old relays can become “sticky” and if this relay is sticking on, then your radio will act like the car is running (it will have its full display on, it will even be able to play music if you turn it on) and things like the light chime will not sound because it thinks the car is running. You may have multiple relays for this sort of thing and only one is sticking on, which may explain why the radio only partially worked, but if this is the factory installed radio and it only has one power feed then this isn’t likely at all.

Another possibility is that the chime circuit has developed a bad ground, and it has found an electrical path so that it is now feeding electricity into the part of the electrical system that is supposed to be turned off by the above mentioned relay when the relay is turned off. It may feed enough power to activate the radio’s displays but not enough to actually power the radio. So this one can happen even if you do have the stock factory radio.

Of course, it is also possible that you have more than one problem here.

You don’t have a fuse problem.

If your roommate can rig something up but not fix it properly then they really aren’t that handy with electricity. Take it to a proper shop or find a friend with better electrical skills. Getting a repair manual for your car from ye ol local auto parts shop (should cost about 10 bucks) will at least give you a wiring diagram to show you what is hooked where. You should be able to measure the voltage at the chime when it should be chiming. If the chime is getting a full 12 volts and isn’t chiming then the chime itself is shot. If you see the voltages go wonky then you’ve got a bad connection somewhere, which doesn’t necessarily mean that the chime is good, but it does mean you have a wiring problem.

Ok - to clarify, it is an aftermarket stereo. I also forgot to mention that the backlight that illuminates the speedometer does not come on when the headlights are on anymore, either. This is controlled by a small dimmer knob to the left of the steering wheel, but that knob is completely useless right now.

The solution I was considering was some sort of timer to just turn the damn lights off after 30 minutes of the car being off, or something like that. She (the aforementioned roommate) knows her way around a wiring diagram, but not around a car. :wink:

When I get home from work (well, first, I guess I need to jump my battery), but I’ll try hooking the stereo back up and see if it fixes either of these problems. (maybe I should check to make sure that the “hey, your key is in the ignition and the door is open!” chime works still, also, since on this car it makes the same noise. I feel like I’m stuck at a correlation/causation crossroads that I can’t resolve from memory due to my own inattentiveness.

I found the owner’s manual, and it doesn’t mention any sort of voodoo involving impossible-to-replicate actions to toggle the chime.

The radio display staying on is almost certainly from a short inside the radio, where the battery feed to the radio’s preset memory is connecting to the display power. Relays are not used in this type of circuit.

The warning chime system is most likely not related to the above, nor the instrument illumination. However, the failure of these items could be caused by their respective fuses, so by all means check for that. If either of these fuses is blown and the new one blows right away, remove the radio, replace the freshly blown fuse(s), and see if they work now. If so, scrap the old radio and get a new one.

This is true for some higher amperage circuits (e.g. radiator cooling fan) and some complexly controlled circuits (e.g. taillight relay in certain Asian cars), but by and large most circuits don’t have relays. Their power supply is directly through the ignition switch.

Something to bear in mind, which I discovered with my own car this week. If you’re battery is running low on charge it can cause weird things to happen with the electronics, which expect a steady 12v. I had two warning lights come on together (while the engine was running), and the next day it wouldn’t start, and trying caused the doors to unlock. I assumed it was electrics, but found all the problems went away once the battery was fully charged.

I figured it out, y’all!

(it was a fuse. D’oh!)

It got much easier to diagnose when I went and bought some fuses anyway, and realized on the way home that I didn’t have taillights, just brake lights. That was apparently one very important fuse!

No problems with the radio, either, FWIW.

A blown fuse took out your tail lights and caused the stereo’s lights to stay on.

The spirit of Lucas, Crown Prince of Darkness is alive and well in your car!

(And this is why I loathe 12 volt troubleshooting!)