The headlight switch/knob is draining my battery. Sometimes.

[ualla]

Hi all,

I recently bought a lovely 1999 2.0L Z3. Apart from having to change the wishbone bushes in a couple of days time due to severe tramlining, the car is in excellent condition. I'm already thoroughly enjoying it

A bit of background:
Last weekend I started making small changes: I changed the footwell speakers and will be mounting the tweeters this weekend. I also added a CD Changer to AUX input to the stock BMW Business CD head unit. The day after I made these changes my battery had died. I thought back and remembered hearing the buzzing sound it makes when you leave the lights on, but dismissed it (stupidly) as the lights were definitely off). I blamed the AUX converter so I removed it.

Last night I went to a friend's house and when I turned the lights off, then I turned the car off, I got that buzzing sound again. I was stumped. I then thought of playing around with the headlight switch and realised that by turning it anti clockwise the buzzing stopped.
Is turning the switch used to dim and brighten the dashboard? It doesn't seem to be working smoothly for me and was wondering whether anybody had experienced anything similar?

I saw a guide on here on how to take the switch apart and though I might give it a go to clean the contacts.

Anybody have other suggestions/opinions?

Many thanks for reading and apologies for the long post.

[Southernboy]

If you switch off and leave the indicator lever in an "on" position..I think the park light in that direction stays on...But if you're hearing the alarm buzzer, then you have a problem switch...Taking them apart is fiddly, but do-able...But if the buzzer is sounding, there must be some lights still on...??
Also, the buzzer shouldn't continuosly sound...it only sounds for a short while, then should stop. As you know, the interior lights all go off after a short period, and this should apply to the buzzer too, even when lights are on and the motor / ignition has been switched off.

[Robert T]

Well that sounds like somewhat of an oddity. The headlight switch incorporates a rheostat (dimmer) for the instrument backlights - these are prone to a build up of dust and can go intermittent in that when you rotate the switch, the lights go out then come back on again. The buzzer is there to remind you that you have left your lights on, so it is tied into the headlight switch, but it should be on the switch circuit, not the instrument backlight circuit.

You say that you have been working on the stereo, and I am wondering if you have either disturbed a connection, or connected something up incorrectly. On my aftermarket headunit, the backlight dims when I turn the headlights on (it doesn't need to be as bright when it is dark outside). I am not sure whether the BMW headunit does this, or whether it even uses the rheostat to give a variable lighting level, but it will be connected into the lighting circuit somewhere. Now if you have somehow connected something on the back of the stereo/amp/CD player into this circuit, and it is supplying current even when the ignition is off, it might well trigger the headlight buzzer. It would also account for your flat battery, as there would be a permanent current drain.

This is of course all pure speculation on my part, but it does at least sound plausible.

Cheers R.

[ualla]

First of all, many thanks for the replies!

@Southernboy, I hadn't thought about leaving the indicator lever in an on position. I will double check that tonight, but I am quite confident that wasn't the case. The buzzer itself sounded for about double the time that it usually sounds for when you leave the lights on. It's not infinite, but it is much longer... One thing that I forgot to mention is that when the buzzer was sounding, the digital mileage display was still on as well. Not sure if that makes a difference.

@Rober T, I definitely get the intermittent on-off when turning the dimmer, so it must be dusty. I haven't noticed whether the head unit's backlight dims when I turn the lights on, I will check that as well. I also did think that maybe I had reconnected something badly, but seeing as it is a straightforward connector I'm not really sure what I could have connected incorrectly. Further to that, I don't have anything connected to the back of the head unit anymore and it still gave me that buzzer warning. When I called the AA, the guy also checked if there was any weird constant battery drain and it turned out negative. There wasn't anything draining the battery (and he also mentioned that the battery was in good condition). Yesterday, a whole day after I had recharged the battery, the car started up fine as well.

I am quite stumped to be honest. I hope that when I get home tonight my battery isn't dead again

Thanks again for your input, much appreciated!

[BladeRunner919]

thing that I forgot to mention is that when the buzzer was sounding, the digital mileage display was still on as well. Not sure if that makes a difference.

That definitely points to a wiring problem, and the fact that you just did a stereo upgrade would have me looking at that as the most obvious cause.

[ualla]

Thanks BladeRunner919, that's what I would have thought as well. The thing is that I didn't actually cut and rejoin any wiring behind my radio. I just unplugged the BMW connector and then plugged the other connector.

Also, I tried starting my car yesterday and it started without problems, so there doesn't seem to be a permanent battery drain.

I do believe that it is the light switch, although I'm still not sure what is causing the light switch to malfunction...

[ualla]

For whoever is interested, the problem is definitely with my light switch. Or the electronics behind it.

I have remounted the AUX converter and the battery hasn't drained. But I used the car yesterday and after turning the lights on and twisting the light switch a little, I got the buzzing again after having switched the lights off. As soon as I turned the switch all the way to the left the buzzing stopped.

All I need to do now is take the switch off and clean the contacts...

[XVar]

If I remember right, to remove the headlight switch you need to pop the end cap off and there's a hidden screw inside it. It's not obvious at all that the end of the switch is removable, just a little pointer to be aware of

[ualla]

Thanks for the heads up XVar! I did notice that on Titan's how-to guide so will definitely make sure I take note of that.

I also wanted to take advantage of this post to thank you for your speaker replacement guide. I bought the V1 Edge 305 set (no separate crossovers, just the capacitor) and was very thankful for your guide. I just need to finish fitting the tweeters tonight.

[ualla]

So, I took my switch apart today and I think there is something very wrong with the spring in the rheostat, when I turn the dimmer the spring bunches up:



I've seen a second hand one on eBay. If it stays at a reasonable price I'll make an offer for it, otherwise I'll just have to be careful every time I use the lights

[gookah]

So, I took my switch apart today and I think there is something very wrong with the spring in the rheostat, when I turn the dimmer the spring bunches up:



I've seen a second hand one on eBay. If it stays at a reasonable price I'll make an offer for it, otherwise I'll just have to be careful every time I use the lights

thats not good at all, It is supposed to remain in place and the switch contact rotate inside it. It is probably shorting against something.
Lucky that didn't cause a fire..

[Brian H]

thats not good at all, It is supposed to remain in place and the switch contact rotate inside it. It is probably shorting against something.
Lucky that didn't cause a fire..

Totally agree, I would replace ASAP.

[ualla]

Cheers guys. I saw this one. It's from a 2.2i Z3, I'm guessing the answer is yes, but will this fit my '99 2.0?

http://www.ebay.co.uk/itm/BMW-E36-Z3-RO ... 3a8c280181

[Brian H]

Cheers guys. I saw this one. It's from a 2.2i Z3, I'm guessing the answer is yes, but will this fit my '99 2.0?

http://www.ebay.co.uk/itm/BMW-E36-Z3-RO ... 3a8c280181

Just cross referance the part number from your switch, It should be OK.

A new switch is only £37.15 from BMW, clicky link

[Althulas]

You just beat me to it Brian but part number confirmed the same for left or right hand drive. Ualla If you go for that second hand part you'll have to transfer it to your plastics as I presume your driving a left hander but for a little extra I would go for the new part and piece of mind.

[ualla]

Hi guys, thanks!

I'm actually in the UK (I've set my location in my forum profile but it doesn't seem to appear for some reason), so I have a RHD Z3.

I looked on realoem, but I couldn't find the diagram for the headlight switch. I now found it on realoem thannks to the part number. I was looking for it so I could also find the part number for the little light bulb that sits under the switch. Does anybody know which categories I'd need to click on to get the light bulb part number?

Regarding getting the new part, I think that might be the better option. For a little bit more I think it is probably worth it. I don't mind using my plastics, it's still in good shape.
@Brian, is that link actually BMW? I've never bought from that site...

Thanks guys for your help!

[Brian H]

Part number 4 below for the bulb. 63 21 7 167 000

Outflow nozzles/covers - BMW parts catalog

Click on the image and it will take you to the diagram and parts list.

The link I posted earlier is an online BMW dealer, try your local dealer and you will get it delivered free of charge. If you do go to your dealers let them look up the part number, if they are wrong they will change it, if you are wrong you have to keep the part

HTH

[Southernboy]

REPLACEMENT SWITCH £.10....
http://www.ebay.co.uk/itm/BMW-Z3-HEADLI ... 4d19990bf3

[ualla]

Thanks guys, much appreciated.

I might just get it new. I'll see how expensive the one Southernboy posted becomes and then make a call.

Cheers!

[ualla]

So I ordered the new rheostat from my local BMW dealer and the new part costs £30+VAT. I will pick it up on Saturday morning and replace it...

[henrycrun]

Has anyone by-passed the potentiometer so that the dash just stays constantly bright ?

[Brian H]

Has anyone by-passed the potentiometer so that the dash just stays constantly bright ?

Not carried this out myself but this is the solution you are referring too.



HTH