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Discussion Starter #1
Sorry about this but i'm probably missing a really obvious fix here.
The clock and the brake lights have stopped working, everything else works as it should. I have checked the fuses and these are all ok, although the box where they sit behing the passenger seat was quite warm inside.
Any advice would be appreciated
 

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Discussion Starter #3
Thanks, forgot to mention the battery also goes flat after a few days, but then it will be fine sat for weeks.

Wheres the earth strap located?

Sorry but i have to ask....
 

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Hi,
A loose Earth is a common problem on the S2.
The Earth strap on the S2 runs from the bellhousing to the body,not too sure on the S4.
Regards
 

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Check the boot light and bonnet light and door switches. If the switch is playing up you could end up with the light being on without knowing. It doesn't matter when using it since it only uses a few Watts, but it could flatten your battery in three or four days. I recently discovered a problem with my delay timer on the interior lights on my S3. The lights weren't coming on, but the timer relay would flatten the battery after a week or so. All caused by the door switch not being pressed in when the doors were closed.......
 

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Am I missing something here....what fuse box behind the passenger seat??? Last time I looked the main fuse box on an S4 is located under the dash on the left hand. The ECU is located behind the seat on the right hand side.

As to power drainage follow andyt's advice. Otherwise its the multimeter and pulling fuses routine.
 

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Am I missing something here....what fuse box behind the passenger seat??? Last time I looked the main fuse box on an S4 is located under the dash on the left hand. The ECU is located behind the seat on the right hand side.

As to power drainage follow andyt's advice. Otherwise its the multimeter and pulling fuses routine.
Good point. Last time I looked, they were under the dash as well!
 

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I had same battery draining problem on my S4. It was the passenger side footwell light permanently on!
The clock and brake light may be seperate problems. The brake light could be the brake light switch not connecting properly under the brake pedal (another problem I had!). My clock never worked :lol:
 

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I had same battery draining problem on my S4. It was the passenger side footwell light permanently on!
The clock and brake light may be seperate problems. The brake light could be the brake light switch not connecting properly under the brake pedal (another problem I had!). My clock never worked :lol:
Yes thats a very common problem. On the S4 the brake light switch can work free and not make a proper connection. If both brake light and clock are not working as well as the electric mirrors and footwell lights the first thing to check is the fuse (that is the one under the dash!) as they are all on the same circuit.
 

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Discussion Starter #11
Thanks everybody,

It seems as though the passenger footwell light was not turning off. So i have fixed that. Battery sorted!
The mirrors, boot light and brake lights are still non workers but footwell lights are fine? is it tracing the wires time?

Stupid question then, Behind the passenger seat in what i called the other fuse box, i have 2 x fuses and what looks like 2 x switch relays. Can you tell me what these are.

Thanks for all your help.
 

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Thanks everybody,

It seems as though the passenger footwell light was not turning off. So i have fixed that. Battery sorted!
The mirrors, boot light and brake lights are still non workers but footwell lights are fine? is it tracing the wires time?

Stupid question then, Behind the passenger seat in what i called the other fuse box, i have 2 x fuses and what looks like 2 x switch relays. Can you tell me what these are.

Thanks for all your help.
Put your lights on and see if the boot light works. I believe S4's where all wired up this way? I would also check your brake light switch which is up by the brake pedal and hidden by the lower kick panel, make sure it is activating.

The other fuse box is the ECU and the fuses are related to this. The relays are to do with the oxygen sensor and a solenoid valve in the plenum to fuel breather system.

hope this helps.
 

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The passenger side footwell light in my S4 was a constant source of flat battery syndrome as passengers invariably knocked the switch whilst getting out.
I have now disconnected it!

Other than that, the only problem I have had was leaving the (removable)facia on the stereo in situ. That seems to drain the battery over a period of a few weeks.
 
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I thought the boot light in my S4 didn't work until I was told it only worked with the side or main beam lights on. Bit daft as I switch them off before turning off the engine before unloading but there you are.
 

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I thought the boot light in my S4 didn't work until I was told it only worked with the side or main beam lights on. Bit daft as I switch them off before turning off the engine before unloading but there you are.

Yep, and if you really want to give yourself a challenge, try and find the switch that turns the boot light off when its closed! I can't find it but I know the light goes out as I put my digital camera in the boot to check it....sad or what!:D
 

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Another source of battery drainage is the alternator regulator. Whereas older alfas had a seperate regulator, the S4 has an integral BOSCH regulator in the 55Amp alternator, that can be slid out of the alternator with, I believe, the brushes as a unit. Check this, and check the brushes while you are at it for uneven wear-If you see one brush much shorter, replace in any case. My Mercedes TE had this problem-not expensive or difficult to replace. A defective regulator allows current to back drain through the alternator.
 

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Discussion Starter #17
Thanks for all your help, all seems to be sorted now, but...... is it normal for the sidelights to come on when you brake? The light on the dash comes on if i'm braking or have the handbrake on. I'm hoping this is normal
 

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but...... is it normal for the sidelights to come on when you brake?
Really not! The side lights come on when you turn them on, the brake lights come on when you press the brake pedal. There should be no other interaction, even in the wacky US they've only managed to confuse brake lights and turn signals. If you only see sidelights lit when you hit the brakes then something is wrongly wired, if you get a bit of a glow from both brake and side lights then you have bad earth.
 

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Just checked out this thread to see what the issue with our S4 lights were. I had an inkling straight away that it was the brake lights staying on even when the ignition was off, which was exactly what happened once we eliminated all the other lights. I checked the switch to the pedal and it wasn't coming back sufficiently to turn off the lights. I don't know if there was supposed to be a pad on the metal flange that presses it, but there wasn't. Anyway, a bit Heath Robinson, but there now is a small pad that takes up that slack and it's now turning off properly. German electrics, eh?! :blah:
 

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Just checked out this thread to see what the issue with our S4 lights were. I had an inkling straight away that it was the brake lights staying on even when the ignition was off, which was exactly what happened once we eliminated all the other lights. I checked the switch to the pedal and it wasn't coming back sufficiently to turn off the lights. I don't know if there was supposed to be a pad on the metal flange that presses it, but there wasn't. Anyway, a bit Heath Robinson, but there now is a small pad that takes up that slack and it's now turning off properly. German electrics, eh?! :blah:

thanks for reminding me I am 9 years older:)

no pad originally.
3 possibilities, imo:
an incorrect length aftermarket switch
or, the switch was not located correctly in the hole it fits into
or, you have a rhd, and the conversion wasn't great (like most)


But you got it working, so that is good.
this is the original switch:
 

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