BMW E36 3 Series 1992-1998 (318i/s/ti, 320i, 323i, 325i/s, 328i/s, M3, conv)
brake warning light in 318ti
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Replies:
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Last Post:
Aug 23, 2011 6:58 PM
Last Post By: jazzsaxman
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Posts:
3
Registered:
01/18/05
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brake warning light in 318ti
Posted:
Jan 18, 2005 8:11 PM
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Does anybody understand the brake warning light circuit in a 1996 318ti? The manual shows a simple circuit of two sensors in series with a light bulb between 12v and ground. This doesn't make any sense because that would require both sensors to fail to get a warning light. And the lamp comes on briefly (normally) at start-up, so clearly the circuit is more complicated.
What is in the sensors? A crystal that gets shattered with any contact with a rotor? Or a simple ground contact? Is there a test for a sensor?
My problem is that the light is on for no apparent reason. Disconnecting the sensors does not extinguish the light. I have not replaced the sensors yet. Could anything else be causing this, such as (rear) brake light problems.
Thanks in advance for any help.
Dick
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Posts:
11
Registered:
07/16/04
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Re: brake warning light in 318ti
Posted:
Jan 19, 2005 9:33 AM
in response to: lovemy318ti
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Check your brake pads; it's likely that either front pads and/or rear pads need to be replaced. Your car probably has 2 sensors (one on the front drivers side and the other on the rear passengers side). If either front pads OR rear pads are worn to the point where the sensor is tripped, you HAVE TO replace the sensor after replacing the pads. Just replacing the pads doesn't turn the warning light (on the dashboard) off.
FYI, the brake pad sensor basically a conductor when rubbed against the rotor, the wire breaks (i.e., continuity breaks). Hence, the dash light comes on.
The dash light comes on (and should come on) for a brief period upon starting the car; that's basically a self test of the circuit/system.
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Posts:
4,772
Registered:
12/09/03
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Re: brake warning light in 318ti
Posted:
Jan 19, 2005 9:44 AM
in response to: lovemy318ti
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The sensor is just a simple loop of wire. When ground through the circuit senses an open. Check with an ohmmeter. Can also jumper the connector at the sensor to check the cicuit.
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Posts:
3
Registered:
01/18/05
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Re: brake warning light in 318ti
Posted:
Jan 20, 2005 12:23 AM
in response to: Charlie
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Thanks for the comments.
The light came on some time ago and I replaced the rear pads, although there was probably 1/8 inch left. The front pads had previously been replaced months before. There was no evidence of any scraping on the rear sensor. I did not replace it.
So a good sensor should show a short betweeen the two pins on its cord? I just today tested one new one (not yet installed) with an ohmmeter (Fluke DVM on the diode test--low voltage ohms test) and it read open. (???)
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Posts:
4,772
Registered:
12/09/03
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Re: brake warning light in 318ti
Posted:
Jan 25, 2005 10:20 AM
in response to: lovemy318ti
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I think they should show continuity between terminals. See diagram.
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Posts:
30
Registered:
10/14/04
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Re: brake warning light in 318ti
Posted:
Jan 26, 2005 9:45 PM
in response to: lovemy318ti
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try to replace brake bulbs by the ORIGINAL bulbs, it happen to me in two of my bmw's (325 i, 325is)
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Posts:
60
Registered:
05/15/07
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Re: brake warning light in 318ti
Posted:
Aug 23, 2011 6:58 PM
in response to: lovemy318ti
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It is a logic control. it is not actually wired this way.
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