Electrical expertise needed please!!

[e34.535i.sport]

Hi!! I'm in the process of fitting a boost gauge to my e39 530d in a similar fashion to this: my $50 boost gauge install - The Unofficial BMW M5 Messageboard (m5board.com) . I have VERY little knowledge about electronics and try to avoid messing with it if possible but I'm stuck in the situation of what I can do with my fog light switch once it is replaced with the boost gauge (already in motion!!) ... If I leave the light switch off the car is leaving the lights on even without the kep in the ignition (I.e it thinks they're permentantly on).

The plan of action I'd like to take is remove the current large round switch and replace it with a smaller inconspicuous one and relocate it much like in that other thread. I hope this isn't a ridiculous question but how can I go about that? Do I have to splice connections? More importantly, the current switch has a weird set up - OFF, ON (front fogs), then a spring-loaded thrid position which puts the rear fogs on but it springs back to the ON position - Can I change this to a simple on/off switch without too much hassle? I've had the intake off this car and everything but the thought of messing with these little wires scares me!!

Please help!! :P

[whiskychaser]

Dont know about electrical expertise but two small problems spring to mind. First is that car builders are really tight with the amount of wire they give you and to make connecting idiot proof the wires normally terminate in a plug. Murphy's law says there wont be enough wire to relocate the switch and the plug wont fit your new switch. I think the switch is a combination of an on/off and what I believe is called a 'momentary' switch. They are pretty common but I am not sure if you will get a very small one. Ideally you want the colour to match the other switches. Maybe try Maplins or RS?

[e34.535i.sport]

Thanks Colin - This install has become a bit of a nightmare to be honest! I can't get a boost reading anywhere and apparently would have to tap into the inlet manifold to get a reading... I doubt that's going to happen. I do get a vacuum reading on it though so all is not lost I suppose, yet I connected at two different points looking for boost and got two different readings! One said ~27in.hg and the other said ~15in/hg... Not sure if there's a leak somewhere and only one side is affected?

Anyway the boost gauge fit perfectly into the fog light switch position which is lucky! And the good news continues! I bought a replacement switch as you suggested from maplin today but could only get a rocker switch, simple on/off as I don't mind if the front/rear fogs go on/off at the same time - that's better infact! Now the old switch has 4 wires going to a connector (which I will cut off)... From what I read on another thread they are: 1. Earth. 2. Lighting for switch. 3. Front fogs on. 4. Rear fogs on. Does this sound reasonable? The NEW switch has three prongs on the back (similar to this : Slim Line Rocker Switch : Rocker Switches : Maplin Electronics but with three connecting prongs) so can I connect earth to 1 prong and both the front and rear on wires to another prong and blank off the lighting wire? (New switch has no light and looks like standard BMW material - Nice and stealthy!).

Oh and I think I'll have just enough slack!! Just!! :P

Cheers for the assistance mate!!

[whiskychaser]

I suppose it depends where you connect to but I wouldnt fancy tapping into the manifold either :-( I have the Bentleys for the E39 but not the wiring diagram part :-( I am not sure if, when you press the momentary part of the switch, it triggers a relay for the rear lights and if there are any consequences with keeping that switch closed. Maybe none as when you turn the switch off completely the lights all go out lol. I am a bit surprised the OBC doesnt show you what boost you have as any half decent truck displays it. That would be too simple though wouldnt it :-)

[e34.535i.sport]

I suppose it depends where you connect to but I wouldnt fancy tapping into the manifold either :-( I have the Bentleys for the E39 but not the wiring diagram part :-( I am not sure if, when you press the momentary part of the switch, it triggers a relay for the rear lights and if there are any consequences with keeping that switch closed. Maybe none as when you turn the switch off completely the lights all go out lol. I am a bit surprised the OBC doesnt show you what boost you have as any half decent truck displays it. That would be too simple though wouldnt it :-)

I've stumbled on an idea regarding the boost gauge, but not 100% sure how to pull it off!! Have you heard of swirl-flaps in the e39 manifold? I'm sure you will have, it's a major issue - Hence I removed them from the underside of the manifold a good while back and replaced with some blanking plates to be safe... I read somewhere that it's possible to drill a hole in one of the blanking plates and hook the boost gauge up to it - Direct lnk to the manifold vacuum and boost without risking breaking the manifold!! Sounds good to me... Yet, I don't know how I would Get a nipple onto the blanking plate that would be suitbale for the boost gauge??? What you reckon??!

Hmmm... The switch thing is sounding complicated! It's more annoying seen as the messing has been for no reason so far , yet the swirl-flap plan is a definite-maybe! I might try to relocate the original switch lower down the dash, that way I don't have to worry wbout wires etc... It would look better though I feel if I could use the smaller switch I have. :S

Haha I wish the OBC would give me that info!! I'm even considering buying some software/hardware for live data but with the baby on the way I'm not sure I should spend that kind of money!!! :P

[whiskychaser]

I've heard of swirl flaps but didnt realise that if you took them out they left a damn great hole in the manifold:-) If that is so, no wonder you plugged the hole! If thats the case you could simply get hold of some threaded nipples, remove the blanking plates and drill the out to fit the nipples and presumably tighten the nipples with a nut on the inside?
Call me conservative. No. Call me a coward but I would use the old switch if poss. It works, is designed for and fits the car. I know your new switch must have cost at least 50p but this is a learning process :-)
It would be interesting to find out if my kit works on diesels. If it does, maybe thats something for the future for you? Granddaughter's birthday this weekend but will have to pop over before you are pacing up and down at the hospital :-)

[shogun]

I have the Bentleys for the E39 but not the wiring diagram part

E39 wiring diagrams: have you checked here, WDS E39?
WDS BMW Wiring Diagram System - Model Selection

[whiskychaser]

E39 wiring diagrams: have you checked here, WDS E39?
WDS BMW Wiring Diagram System - Model Selection

Many thanks for the link! Added to my favourites :-)

[e34.535i.sport]

Thank you VERY much Shogun - I've had a look at it and found some info - Hopefully I will be clever enough to figure out the next move! (I'm not holding my breath!) - I can see the fog light switch and it says 0) Fog lights off
1) Fog lights on
2) Rear fog lights on
3) Front and rear fog lights on

Other than that I'm lost!??? There are four wires so poss this explains what each one does, but only 3 positions on the switch.

Whisky, I'm very tempted to employ the old switch but I'm going to struggle to get it in a new position neatly. On the positive side I have another swirl-flap blanking plate now that I'm taking into work and a tech guy is going to drill and tap it with thread for me! I've just ordered a nipple of ebay too so I'm on my way!! At least if I can get it working it'll have been worth all this hassle!!

Haha defo mate, be good to see you again Not long now before I won't have time to mess with the car, I'll have my hands full with dirty nappies! :P ha!

[whiskychaser]

I am very old fashioned. I'd use a multi meter and find out what contacts are made when you throw the old switch :-) Drilling and tapping the blanking plates sounds like the way to go. Are you thinking of using any sort of sealant for the threads?

BTW. Have you ordered one of those models that sleeps through the night? We never had one but they are highly recommended :-)