Homer

iTrader: (1)

My Camry has one of those stupid seat belt buzzers that come on every time you put the key in the ignition. There's a switch in the seatbelt that tells the buzzer to shut off when you buckle the belt or after a few seconds. I've thought about completing the circuit so the car thinks I'm always buckled and shuts up, but I'm worried that would drain the battery. I'm suspecting the circuit is still live even when the car is parked because the power seat works without keys also (too bad the @#$% power windows don't!). I don't want to just gut the buzzer because it's the same buzzer that tells you when you're doing something stupid like leaving the keys in the ignition (I'm not the only person that drives the car). Any advice would be appreciated.

Stuart Moss

No. If I understand your intention, I could ask you if the battery would have any additional drain ("go dead") by simply having the seat belt permanently buckled. Again, "no". With the key out (ignition "off") the power to this circuit should be disabled. The seatbelt circuit is simply an input to it.

I'd guess that there would be a single wire going to a switch someone in the seatbelt mechanism. Keeping this wire grounded would fool the circuit to think that the seat belt is (always) connected. I doubt that it's the reverse - keeping it "open" (not grounded). The hard part, of course it to find this wire.

Of course, without actually seeing the circuit, all the above is just an "educated" guess...

Homer

iTrader: (1)

I guess I should have mentioned that I already had found the wire to the seatbelt. Luckily, It has its own harness before it connects to the big harness that powers the whole seat.
Here's what I found out. I unplugged the seatbelt harness, and just for kicks, turned the car on to see what'd happen. To my surprise, the car only beeped at me until the automatic shoulder harness moved into position. So I'm guessing that the seatbelt switch is normally closed, instead of normally open like I thought. Bad news, of course being that there's another one in the shoulder harness mechanism. I think I'll just leave that one alone, at least for now. Thanks for the help!

Stuart Moss

I wouldn't give up so soon. You've already done the hardest part [finding the wire(s)]. If there's only one wire, I'd suspect that it's only being connected to ground. I'm surprised that there is another wire in the shouldner mechanism.

Try grounding one and starting the car. Now try grounding both and start the car.

Nothing? Now try having both un-grounded.

So close yet so far...

Homer

iTrader: (1)

No that's not it. I meant one pair of wires. One in and one out. I unplugged that harness and am happy with the results.
Here's what I did today:
Pulled of the molding cover on the driver's side pillar. Found a four wire harness. Unplugged the harness and found that this is the one for the shoulder belt. two wires go up under the headliner, two go to a switch. The switch is a regular push-button type that the shoulder belt physically pushes in when it gets into position. So I unscrew it from the frame and hold the button in while i turn the car on. No buzzer. Good. Shoulder belt doesn't move. Bad. I go to the harness and try having three out of the four wires connected. No matter which three I pick, the belt either doesn't come back or doesn't go forward. So I follow the four wires under the carpet and they go into a big harness in a circuit board under the kick panel. Well, now what? If I tell the car that the shoulder belt is in position so it won't buzz, then it won't move. I think I'm all done at this end.
I decide then to attack the problem from the other side, the buzzer. So after playing Marco Polo with the buzzer, I find it under the center console, right behind my B&M Ripper shifter (yeah right). The way I figure it, if I've learned anything about the designers of this car today, it's that their not fans of simplicity. Maybe the buzzer has a bunch of wires going into it, from each different place, and all I have to do is figure out which one to snip.
I found the buzzer. It's a blue box with an 18 pin harness going into it. (Side note: While opening up the center console, I found an energizer battery, a reciept for bread and milk from P&C convenient store, and a coupon for OJ that expired in 1992. Oh, and two harnesses that aren't plugged into anything, one a two-wire, one a four-wire. So I unplug the buzzer just to see what would happen, and turn the car on. Did you know that when you unplug the buzzer, the shoulder belts don't work anymore? Now I'm lost. This buzzer box must be some computer control center, or something. When I opened it up, I found a circuit board with buzzer connected to it.
So what should I do? I was thinking of getting a piece of electrical tape or something to cover up each pin, one at a time, to see if I could get it to work that way. Other than that, I think it's about time to throw in the towel on this one.

Stuart Moss

Homer,

Well, you're doing good. I like challenges. Wish I was there to see it.

The two other wires that leave the four wires probably go to the dome light (strickly a guess).

The buzzer probably does not operate directly from each input such as the headlight's on/seatbelt unconnected/ignition key in/etc. In other words, the circuit for the buzzer accepts a signal from an input (either a ground or a positive voltage) and then electronically triggers the buzzer/chime.

You could find the signal from the seatbelt switch on the circuit board and then (maybe) defeat/bypass it. I presume that it's beyond your abilities.

No problem. I think that you can do it at the belt mechanism, which should be easier.

If I understand correctly, when you removed the switch and held the contact in, the warning buzzer did not come one, just like you wanted. Unfortunately, the seatbelt mechanism did not work. It seems something about the switch itself "interfaces" with the seat belt mechanism somehow to enable it to work.

Try replacing the switch but keep the wires disconnected from this switch. Connect the two wires that go to this switch together.

Does the seatbelt mechanism now work normally?

Is the buzzer/chime silent with the seatbelt unconnected?

Homer

iTrader: (1)

Those two wires don't go to the dome light. They're connected to the belt mechanism somehow because if they're not connected then the belt doesn't move forward (when you open the door and want out). If you disconnect the switch, then it moves forward but not backward. So all four are related to the mechanism. This I've found out.
I know what you mean when you say the buzzer only operates from one input. That makes sense. The circuit board interprets the signals from various places and tells the buzzer chime/don't chime. I'm right with you there.
Correct me if I'm wrong here, but you're suggesting I cross the wires that go to the switch, closing the circuit manually. Well, unless there's something to the switch, then it only does one of two things; opens or closes the circuit. I've already tried both via the switch. Switch depressed; no buzzer, no belt action (car "thinks" the belt is already in place). Switch open; buzzer, belt action. I'll try what you said, but I believe that connecting the two wires will close the circuit the same way as the switch will (don't know whether it's a normally open or normally closed type) I'm convinced that the same signal operates the motor and the chime. So we have to go upstream to where they seperate, right? I think that would be the circuit board in the center console that contains the buzzer.
Now I'm willing to guess that the wires going into the buzzer box are the same unprocessed signals from the switch. Meaning it's the same no-buzzer-no-belt game as before, and my only option lies on the circuit board. As you've guessed, I am a rookie to electronics. All I see is a green board with seemingly random distributions of capacitors and microchips.
What should I look for? Where would you look for the signal to the buzzer that's just from the seatbelt, not from the door or ignition? If I go to far upstream to the buzzer itself, I'll deactivate the buzzer completely (might as well just remove the buzzer, which isn't what I want). But too far downstream, and the motor/chime signal hasn't seperated yet. I'll look at the circuit board in greater detail again tomorrow, for tomorrow's another day. (I haven't looked at the car since the last post).
Later,
Homer
P.S. If all automotive endeavors are this ridiculously complicated, I might just abandon my dream project of a big block metro.

Stuart Moss

Ok, I think I understand now. Four wires go to the belt mechanism, two to a switch, and the other two to perform a task inside the seatbelt mechanism.

Also, I didn't realize that this was a moving belt. I thought that only the retractor would/would not move. I hate those types of seatbelts .

I don't understand what you said by:

and then said:

When you say "disconnect the switch", do you mean physically remove it from its mount or remove the two wires going to it?

The first quote stated that removing the two wires would not allow forward movement of the seat belt. So will they move backward?

The second quote stated the disconnecting the switch (the wires?) will allow forward movement, but not rearward.

So what happens when you connect the two wires together that were connected to this switch? The switch itself can remain attached to where ever it is mounted.

I would hazard a guess that the other two wires (not the ones going to the switch) go to a motor on the seatbelt track to move it forward or rearward. Those two wires would have to remain attached. I would guess that when the ignition is first turned "on" that the circuit sends a timed voltage to these two wires to bring the belt rearward. Then (I'm still guessing) when the ignition is turned off, the same circuit will again send a timed voltage to these two wires except reversing the polarity so the motor operates in reverse, allowing forward movement.

Since the buckling operation is fully automatic, I don't understand the reason for the switch. Not using the seat belt is not an option, right?

With a normal seatbelt, the switch would be in the buckle receiver, so a switch there could determine if the buckle was or was not inserted.

Stuart Moss

Another thought. Correct me if I'm wrong, but if the seatbelt action is fully automatic, so the driver cannot elect to NOT use the seatbelt, then I wonder why the chime sounds at all!

On a car with "normal" seatbelts, the chime sounds to "remind" the driver to buckle the seatbelt. When the seatbelt is buckled, the switch in the buckle receiver tells the circuit that the seatbelt is on, and to stop the chiming.

Since your seatbelt is automatic (did I tell you I loathe those types?!), I am now thinking that this switch you found is to tell the circuit that the seatbelt is at its "home", or forward position, and is ready to cycle into its engaged or secured position. That would explain why the belt does not operate normally when the wires are not connected together.

Switch depressed = no buzzer or belt operation because the circuit thinks the belt is in the rear (secure) position????

Switch open = normal operation because the circuit thinks that the belt is at the "home" or forward position???

If the driver cannot decide not to use the seatbelt in this vehicle, then I would ask why the chime? Is it just to warn you that the seatbelt is moving to the rear?

Can you have the seatbelt permanently in the rear position, and then manually fasten it when you want to use it? If so, this could be an option since you stated that you were able to eliminate the chiming, but the belt would not move.

Other than that, the easiest way to eliminate the chime (at least for me) would be to put in a simple/inexpensive "start-up delay" circuit that would inhibit the buzzer for say 2-3 seconds upon starting the car. It would be childsplay" to make this circuit for <$8.

Homer

iTrader: (1)

I'm not good at explaining things. I'm just not. Seeing something is 1000% better than hearing/reading it, so let me try to explain.

This is not the seatbelt (lap belt). The seatbelt is fully manual. there are two wires running into the seat buckling mechanism. I disconnected those two wires (fortunately they had their own harness, which I just unplugged) several days ago. No problems there. Originally (stock) the car would beep for maybe 10 seconds if the belt is unbuckled. If you buckle in, it stops beeping.

Now that I've disconnected that harness, it only beeps for about three seconds (the length of time it takes for the automatic SHOULDER belt to get into position). I was ready to call it quits there and accept the compromise, but somebody (I think his name was Stuart Moss ) encouraged me not to quit and go on.

So the lap belt is totally seperate from the shoulder belt. The lap belt is fully manual, and the shoulder belt is fully automatic.

Let's talk wires now. The shoulder belt has four wires, two going to the switch, and two going up under the headliner. Here's what I did.

Experiment 1: switch connected (wires intact), "other" two wires disconnected.
Result: No movement, forward or back. "Other" two wires must be for motor. Reversing polarity causes reversed action. (I was wrong in yesterday's experiment, I mixed up my wires. Ignore what I said in previous post. What I disovered yesterday is that disconnecting one motor wire disables one direction, but not the other) So the "other" two wires go to the motor.

Experiment 2: wires disconnected from switch, motor wires connected. shoulder belt moves forward when door is opened. Does not move backward when door is closed, keys in ignition, turned to "on".

So I need all four of those wires. Today, I disconnected the wires to the switch, and manually connected the two wires together, like you suggested yesterday. Here's what happened. Shoulder belt moves backward. buzzer goes off. Buzzer continues to go off after belt is in position. (So it's a normally closed switch, right? The belt opens the switch when it gets into position, stopping the motor and buzzer)

Another experiment: I unscrew the switch from the frame, hold in my hand (all wires intact at this point). I turn the key to "on." As long as I don't push in the button, the belt moves and the buzzer goes off. When I push in the button, the buzzer and belt both stop. I let go, they both continue.

The purpose of the switch (apparently) is to tell the car (computer or whatever) that the shoulder belt is fully back (in driving position) or it is not. Interestingly enough, when I disconnect the wires to the switch and connect the wires manually, the belt moves just fine and stops when it reaches the end of the track. I don't hear a hum of the motor continuing to push. And I don't believe that there's a switch for the other side (fully forward) either.

So take the switch out of the equation, right? That won't work. If I remove the switch, and close the wires, the belt operates as normal, but the buzzer goes off even AFTER the belt is in position. If I leave them open, the buzzer never goes off, but the belt never retracts either, even though the motor wires are intact.
Maybe now everything will be clear as mud.

Homer

iTrader: (1)

Yeah, we're on the same page now. I've asked myself what the point of the chime is for the AUTOMATIC shoulder belt too. Must be a warning that the belt is coming. "Look out! It's the belt!" Or maybe they didn't bother to reengineer different circuits for cars that had automatic belts from ones that didn't. This circuit would make more sense if it was a manual belt.

I know what you're talking about, but no. You can't unbuckle the shoulder belt. My Dad's Talon has auto shoulder belts with buckles, but this car does not.

I'm interested in learning about this delay circuit. What's in it? How's it work? Is it like a capacitor that just absorbs charge for a few seconds? Sounds like a plan to me, as long as it's not too bulky, because wouldn't it have to be directly connected to the chime (which is on a circuit board stuffed in a blue box)?

If you connect it to the switch, then all we would accomplish is the belt motion and buzzer would be delayed 2-3 seconds. Same irritating buzzer, just a pause before it and the belt are activated.

Stuart Moss

Homer,

Ok, I got it. I still believe that that switch you described is just to tell the circuit when the seatbelt is in the driving (rear) position.

Regarding the two other wires to the motor - perhaps the motor is grounded on the chassis, and the motor will operate either forward or rearward based upon which of the two wires is providing voltage.

Because you were able to disable the manual lap/belt switch by removing it, I think that that's all you can do to stop the buzzer, at least from the seat belt end.

I would think that removing the lap belt wires would have (should have) kept the chimer silent. But since you still see ~3 seconds of chime, I doubt that there's anything more you can do, at least with the seat belt mechanism side. Could this just be a bad design for the chime circuit?

Just for "giggles", try connecting the two wires together from the lap belt switch. I would suspect that the chime would revert back to the 10 second (seat belt not connected) cycle. If you are feeling "adventerous", you could try grounding each wire, and then both wires, and see if the chime completely remains silent. But this could damage something depending on the circuit. Underscore "adventerous".

On my mothers Camary, they would always remove the ignition key when parked at home, throwing it on the counsole, to keep the chime silent when opening the door. I would only remove the key about 1/4" to keep the chime off when opening the door.

I later put a piece of electrical tape over the chime/buzzer to make it quiet. It attentuated it enough so that it'd only make a very muted "ding-ding". Of course you could remove the chimer by unsoldering it to keep any sound from coming. But then somethimes you may want to hear it (key in the ignition or lights "on" if it has that function...), or when you want to sell it, it'd be easier to bring it back to "stock" by just removing the tape.

I remember the chime circuit in my mother's Camry, and it was farily complicated. Without a schematic, I would not suggest playing with or modifying the circuit. If you don't want to hear the chime, use the electrical tape trick or use a little silicone and apply something over it to mute it.

Darn Japs......

[This message has been edited by Stuart Moss (edited August 07, 2001).]

Homer

iTrader: (1)

I'm not really feeling any more adventurous. Who knows what I could blow if I ground the wrong wire. My headlights maybe (I probably need those).

Are you an electrician by trade? I notice you're all over this board. Anyway, thanks for all the advice.

What did we learn today? First, electric anything is a pita to do anything with. Second, the KISS principle is strictly an American phenomenon. And third, if you want Camry advice, don't go to a Camry website unless it's a question about changing rims or fart pipes (Yeah, I tried going there first. Silly me!).

Thanks Stuart! (Huh huh, Stuart's cool!)

Stuart Moss

Homer,

I totally agree with the KISS principle.

I'm sorry that we couldn't eliminate the chime. Although you were able to disable it as much as possible without having to go into the circuit. The 3 seconds it sounds even with the lap belt "connected" I think is just the way the circuit was designed.

I've been actively involved with electronics since about 1973, and started working for the Federal Government since 1977.

//Stuart