[V8] No rear brake light wackyness
Scott Simmons
indischrot at gmail.com
Wed Oct 10 15:25:56 PDT 2007
According to the wiring diagram... power comes from terminal 30 (battery
power) to the 25 amp fuse (fuse #3?) which does the horn relay too, I
guess, hm...
After that, it leaves the fuse box and goes directly to the brake light
switch. If your test light or DMM is on a good ground, you should have
at least 12V there (red/blue). If you don't, then check for continuity
between the red/blue wire and the output end of the fuse.
How? Remove the 25 amp fuse. Check to see which side of the slot
(where the fuse goes) is input (12V from battery) and which side is
output (no voltage, no test light lighty up). Set your DMM to the
lowest ohm setting it has (usually 2 ohms or similar). Place one of
your DMM leads into the output side of the fuse's slot and the other
terminal into the plug at the brake switch where the red/blue wire comes
in.
A good wire will show <1 ohm. This verifies the quality and condition
of the wire between the fuse and the brake light switch.
I can attach a quick drawing of what I mean if you like, I know I'm not
explaining this very clearly.
~Scott S.
Ron Wainwright wrote:
>Ok, comments inserted below.......
>
>--- Scott Simmons <indischrot at gmail.com> wrote:
>
>
>
>>The brake light switch gets its power from a 25 am
>>fuse, through a
>>red/blue wire to the switch, and red/black takes
>>that power ..er..
>>elsewhere. Verify 12V at the red/blue wire on the
>>brake light switch
>>(at the pedal). This power is also going to the
>>Shift Lock warning
>>buzzer... so is that the one that yells at you if
>>you're in drive and
>>open the door?
>>
>>
>
> I checked for 12v at the switch as you said & it's
>not even close...but I could be doing it wrong.
> Shift lock warning...this is on my Grey 5spd.
>
>
>
>>As far as brake switch failures, if they don't back
>>out then the problem
>>is usually a bad spring on the inside that doesn't
>>let the button pop
>>out and doesn't connect the two lines, thus no
>>lights.
>>
>>
>
> Spring is fine, in the one I pulled & in the one I
>replaced it with.
>
>
>
>>Dumb question: You checked continuity on the bright
>>filiment on both
>>bulbs, right?
>>
>>
>
> I checked the rear bulbs inside the trunk & the test
>light lite up
>
>
>
>>Another dumb quetsion: You checked for 12V at both
>>terminals in the
>>bulb socket, right?
>>
>>
>
> Again yes
>
>
>
>>In sum: check for 12V at the red/blue wire at the
>>brake light switch.
>>
>>~Scott S.
>>
>>
>
> Well as I mentioned I did & it wasn't even
>close...again, that is if I did it rite. The reading
>was going up & down...but was all way's under 005.0
>with the meeter set at VDC.
>
> HELP.
>
> Ron
>
>
>
>>Ron Wainwright wrote:
>>
>>
>>
>>>You know how I'm stupid whenh it comes to
>>>this......how would I "jump the switch"?
>>>
>>>Ron
>>>
>>>--- Scott Phillips <Scottp at ippe.com> wrote:
>>>
>>>
>>>
>>>
>>>
>>>>Ron.. if you just jump the switch the lights
>>>>
>>>>
>>should
>>
>>
>>>>come on
>>>>
>>>>Scott
>>>>
>>>>-----Original Message-----
>>>>From: v8-bounces at audifans.com
>>>>[mailto:v8-bounces at audifans.com] On Behalf
>>>>Of Ron Wainwright
>>>>Sent: Wednesday, October 10, 2007 3:46 PM
>>>>To: Ingo Rautenberg
>>>>Cc: v8 at audifans.com
>>>>Subject: Re: [V8] No rear brake light wackyness
>>>>
>>>>Ok, again I just checked the Black switch & with
>>>>
>>>>
>>the
>>
>>
>>>>pedal pressed in or not the circuit tester doesn't
>>>>light up.
>>>>So I'll replace the Black switch & see what
>>>>happens.
>>>>
>>>>Thanx
>>>>Ron
>>>>
>>>>--- Ingo Rautenberg <ingo.rautenberg at gmail.com>
>>>>wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>Ron, I believe the black one is for the brake
>>>>>
>>>>>
>>>>>
>>>>>
>>>>lights
>>>>
>>>>
>>>>
>>>>
>>>>>and the clear is
>>>>>for the cruise control interrupt switch. The one
>>>>>for the brake
>>>>>lights works such that when the brake pedal is
>>>>>depressed the switch,
>>>>>which is normally closed, is opened and when open
>>>>>the contacts inside
>>>>>are closed. So make sure you're checking the
>>>>>
>>>>>
>>>>>
>>>>>
>>>>right
>>>>
>>>>
>>>>
>>>>
>>>>>way! Usual
>>>>>failure mode IME is the brake lights don't turn
>>>>>
>>>>>
>>>>>
>>>>>
>>>>off
>>>>
>>>>
>>>>
>>>>
>>>>>-- and that's
>>>>>because the hold-down nut is worn and the switch
>>>>>closes the circuit
>>>>>and the brake lights stay on all the time. I
>>>>>
>>>>>
>>>>>
>>>>>
>>>>haven't
>>>>
>>>>
>>>>
>>>>
>>>>>seen the actual
>>>>>switch fail either. But that's from memory. I'd
>>>>>check but I broke my
>>>>>right leg tibia bone Sunday afternoon. No
>>>>>driving/wrenching ANYTHING
>>>>>for me for a while :-(
>>>>>
>>>>>Ingo
>>>>>
>>>>>On Oct 10, 2007, at 3:18 PM, Ron Wainwright
>>>>>
>>>>>
>>wrote:
>>
>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>I did check the switches at the back of the
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>brake
>>>>
>>>>
>>>>
>>>>
>>>>>>pedal...there's a Black one & Clear/White
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>one..which
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>do I check. But anyway....
>>>>>>...I put a circuit tester on the wires there &
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>the
>>>>
>>>>
>>>>
>>>>
>>>>>>circuit tester doesn't light up..as I mentioned
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>in
>>>>
>>>>
>>>>
>>>>
>>>>>my
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>original post.
>>>>>>But not sure why those would be bad...I've
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>never
>>>>
>>>>
>>>>
>>>>
>>>>>had
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>to replace them in any Audi I've owned.
>>>>>>
>>>>>>Ron
>>>>>>
>>>>>>--- Ingo Rautenberg <ingo.rautenberg at gmail.com>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>>Ron,
>>>>>>>
>>>>>>>Did you check for continuity in the circuit
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>from
>>>>
>>>>
>>>>
>>>>
>>>>>the
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>>brake light
>>>>>>>socket to the brake light switch? That'll tell
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>you
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>>if there's a
>>>>>>>problem in between. You may indeed have a bad
>>>>>>>switch (you should
>>>>>>>have plenty of spares in your depot).
>>>>>>>
>>>>>>>Best of luck.
>>>>>>>
>>>>>>>Ingo
>>>>>>>
>>>>>>>On Oct 10, 2007, at 2:44 PM, Ron Wainwright
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>wrote:
>>>>>
>>>>>
>=== message truncated ===
>
>
>
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