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Discussion Starter #1
There seems to be an awful lot of automotive "in the know" guys on this board. Got a question for ya. I've got a '96 Buick Skylark that has an interesting problem when the brake pedal is depressed. Recently, (and it only does this when the car is moving), when the brake pedal is depressed there is a rather noticable "clicking noise" that sounds as if it is coming from behind the dashboard. And for every "click" that occurs, the headlights dim quite a bit. Once the car slows to a stop, the noise quits. No dash warning lights are showing. Any ideas on this one? Bad brake light switch (rear brake lights work fine), ABS wheel sensor(s), bad chassis/engine ground? Any help would be greatly appreciated :confused:
 

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Does the speed or rate of the clicking vary with the speed of the car. I.E. as the car slows down, does the clicking get slower too?
 

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Discussion Starter #4
PWSchuh said:
Does the speed or rate of the clicking vary with the speed of the car. I.E. as the car slows down, does the clicking get slower too?
Yes,it does seem to be related to vehicle speed
 

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if it only happens when the brake pedal is depressed, maybe signing it a song, hugging it, or saying supportive things to it will help the depression....sorry, i couldnt resist

on a serious note, It almost sounds like the ABS ECU isnt getting its supply voltage. The ABS ECU should have 3 input wires-power, ground, and brake switch. if The power wire isnt working, the ECU will power up with the brake switch voltage, but that voltage is also doing other things, so it does create a draw that could explain the headlight diming. Of course this is just where I would start diagnosing it, there are too many possibilities to diagnose it exactly without being at the car. Good luck!!!!
 

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eyecandy, wouldn't the brake light come on if there was an electrical problem with the ABS ECU? It does seem to the most likely place to start though. If it is bad it should generate an error code shouldn't it?
I hate electrical problems more than anything else. I had a 89 Mustang once that would never start in the morning. Sounded like it was not getting any fuel. Turned out that condensation was getting into the kill switch for the electric fuel pump. Once the weather warmed up a bit it went away which is why I could never find the problem when I would work on the car when I got home.
 

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need a little more info:

What kind of clicking sound is it? a loud metal to metal click? a relay type click? does it get louder when you slow down? quieter? same tone/pitch click?

Does it do this clicking sound on hard acceleration? hard turning?

From what you describe can only think of 2 things right now

The ABS Module or the ABS Pump

The ABS Pump is under the hood (and if i remember correctly, actually on the driver side frame rail near the nose of the car) But you might not actually be able to hear that.

The other suggestion, and more likely suspect due to the fact you can hear it, is the ABS Module (ABS ECU as eyecandy stated) If it is going bad, the relay's will start clicking away trying to activate the ABS Pump, which in tun would cause a significant power loss to the head lights (but sometimes headlights arent always a good indicator of voltage, as i know on my Toronado, when i turn my turn signal on my dash and headlights blink ever so slightly)

The ABS Pump is always on, so you might not of noticed how dim your lights were before, but now that the ECU is possibly messing up, the headlights are more then likely brighter than they were before, but now when the ECU tries clicking on, it is dropping the headlight voltage down to where it used to be, but makes it look like its dimming.

Best bet would be to get someone with a good ear to ride with you and put an ear to the dash and see if he can get a rough idea where the noise is comming from, and possibly have him stand outside of the car while you drive by braking to see if he can hear it from the outside.

Only things I can suggest with the information givin to me

PS. Get in the car, turn the key on but don't start the car... does the ABS light come on? It should... simple bulb test. you never know, the ABS might trying to come on... but have a blown bulb
 

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Discussion Starter #8
It's not a metallic "clicking" of any kind. Sounds like a typical relay "click" but is quite loud. (This may be why it sounds as if it is coming from behind the dash, but may actually be under the hood).

The car is quiet during acceleration & cornering.

When the key is turned on/or the car is started, the "ABS" dash light is lit,then goes out as it should.

Funny thing is, there is no "clicking" noise when the car is first started & driven,probably no more than 50ft. After that distance, whenever the brake pedal is depressed,something starts to "Click".

The speed of the "clicking" seems relative to the tire rotation speed. The faster the car is moving when the brakes are applied, the faster the "clicking". Same principle as when the car is slowing down.

No "clicking" noise as the brakes are applied when the car is in reverse.
 
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