Dome & Map lights not working after mod. Thoughts?

[Gator GT]

I added 4 Superflux LED lights onto the dome light circuit (underhood MB Fuse #8; 20A) to be used as footwell lighting, front and rear. Here is the product: http://www.oznium.com/prewired-superflux

 

They consume 80mA each & a resistor is pre-wired into each Superflux LED light pigtail and those are rated at 2W & 150ohms.

 

 

I cut into connector R50:6 which is a LR wire (blue w/ red tracer) and is the feed to the dome and map lights. It is found in the passenger A-pillar on my 07 B. I soldered the positive lead for the LED assembly onto the wire coming from the connector. I then soldered the wire coming back from the LED assembly (ground) to the wire going up to the dome light (and subsequently, the map lights, since they are on the same circuit).

 

Got everything soldered up and taped. Re-insert MB Fuse #8. Open the door and when I switch the dome light to "ON" and/or "DOOR", all 4 of the LEDs come on, but the dome light will not. It worked prior to the mod, I checked it.

 

And the map lights won't work either.

 

Here's the kicker: the LEDs in the footwell areas dim to 50% when all doors are shut, and after the prescribed time, they fade like designed from the factory.

 

 

Here's where I'm stumped: If MB Fuse #8 was blown, the LEDs shouldn't work.

 

If any cabin fuses were blown that are associated with the dome and map lights, the LEDs shouldn't work.

 

If the Body Integrated Unit was fried, the "dimming theater feature" shouldn't work.

 

 

Thoughts? Advice?

[CzarDestructo]

I'm still not 100% sure of what you did when you wired it up. What did you use for ground, the black cable or the black/brown? I assume black/brown if its dimming? Did you physically cut the wire and put the LEDs in series or did you just cut away at the shielding and solder it onto the bare wires?

 

edit: actually now that I think about it you must have cut the blue/red wire and hooked the LEDs in between the dome light switch and the power source, correct? And did you daisy chain all the LEDs in series or parallel? Series would wiring up one LED's negative terminal to the positive terminal of the next, so on and so forth. Parallel would be attaching all the LED's positive terminals together and negative terminals together.

 

If you did in fact hook the LEDs in between the dome light by cutting the blue/red cable and hooked the LEDs in series, the easiest fix would be to wire the LEDs in parallel.

[Gator GT]

The LEDs are wired in parallel, and they all work. The vendor states that if this particular LED is wired in series, they won't work.

 

I did install the LED assembly between the dome light and power source (MB Fuse #8) by cutting the Blue/Red wire.

[CzarDestructo]

You wouldn't happen to have a multi-meter, would you? What worries me is that the web site says this 'super bright' LED is actually just four LEDs on a chip, potentially wired in series internally. If this is the case, which it sounds like it is, then thats you're problem. LEDs by nature eat almost 2 volts, this is necessary to turn them on. If you wire four in series you're only leaving 4volts for the dome and maps lights which isn't enough to turn them on.

 

If this is true your only option with these particular LEDs is to wire them in parallel, which wouldn't work the way you were hoping. Either way, if you can get a meter measure the voltage drop across all the LEDs when the doors are open. That will tell you everything.

 

I work in Manchester during the day if you need help figuring this all out. My email is my user name @ gmail.com

[Gator GT]

Thank you Czar.

 

I do have a multi-meter, and would have attacked this with it if the rain didn't start.

 

But I did wire them in parallel. And they are working as I hoped, its just that the dome and map lights don't work. I can use the dome light switch to control the footwell LEDs, its just that the OEM dome and maps don't illuminate.

 

 

I was thinking of replacing the dome and map lights with LED versions, that way they wouldn't need as much as the incandescent bulbs.

 

If the rain lets up tomorrow like it is forecasted to, I'll pull the A-pillar cover and test the V drop.

 

Thanks for the thoughts Czar D!

[CzarDestructo]

I'm sorry I should have been clearer. I understand you wired the individual LEDs properly, in parallel , but inside each of the four dongles you bought there are four LEDs in a cluster. I think THOSE are in series, so no matter what you do there is always going to be a significant voltage drop across those. The only way to verify this is with a multimeter.

 

You don't have to pull the whole a-pillar out again. Just test the voltage across any of the LEDs you installed in the interior. If they're all wired in parallel is the same as taking the measurement across what you spliced in the a-pillar. If your voltage reading across those is more then 2 volts you have problems.

[Gator GT]

Ahhhhh. I tried getting a reading by going to the original A-pillar splice (had to go in there anyway...more on that later) and the meter wouldn't give a steady, straight reading. Up and down and all around....it's a good meter, I know it is.

 

The LEDs are wired in series internally, as the vendor assumes it'd be hard to wire them in parallel at the factory. ??? Who knows.

 

 

Anyway, I re-examined the wiring diagram and decided to continue the wiring for the LED assembly up the A-pillar and into the roof wiring. I spliced RIGHT at the dome light. By taking my splice past the off-shoot for the map lights, I regained those. I still don't have the dome light, but the foot well lighting is controled by the dome light switch.

 

I'm going to AutoZone and getting an LED festoon....we'll see if that does it.

 

Thanks again Czar.

[CzarDestructo]

An LED festoon might do the trick so long as you have sufficient voltage to overcome the initial avalanche voltage necessary to turn the LEDs on, typically 2.0v per LED.

 

How important is the dimming function of the foot well lighting? You could install a relay instead of the LEDs then run the LEDs off of it. This won't affect your current lighting however your LEDs will only bang on and off rather than dim.

[Gator GT]

Importance of dimming function? Vital. No, seriously, I like it that much.

 

If I can figure out the dome light, so be it....but since owning the car, half the time I have it off anyway. If it's stuck that way, pfft, worse things have happened in my life.

 

Thanks!

[OldOneEye]

Based on the description, it seems that the resistor is there to make these work in a 12 volt application (usually they are set up to work at a much lower voltage so the resistor makes it OK at 12 volt) so it shouldn't matter how you wired them up as long as they are all in parallel.

 

I would also check the bulb anyway, there could be some voltage backfeeding through somewhere (you never know, stranger things can happen, have seen it all when mobile electronics is involved.

 

Juan

[CzarDestructo]

Did you try the LED festoon bulb yet? Did it work?

 

If not you can try hooking the LEDs you originally bought in parallel across the festoon. You could also do this with the stock incandescent bulb but I wouldn't recommend it as you'd probably be drawing too much current and might blow the fuse or the control/dimming circuitry.

 

You should still do a wattage sanity check with all the LEDs you're adding as well to make sure you're not over-taxing the stock wiring.

[Gator GT]

Czar, I ordered a 2LED festoon from V-LED.com and it came in on Wednesday. IT WORKED!!! Why the filament festoon didn't work (either direction, I did check for polarity on those), is beyond me.

 

And the theater effect is still working too!

 

The wiring the came with the LEDs that I used for floor lighting is 26AWG...fricken tiny stuff. Car's wiring is 18-22AWG, so no red flags are going up in my head...but that's not saying much.

 

I did have the door open and the map lights on and nothing blew. If I do have the doors open for a period of time more than just ingress/egress, I usually shut off the circuit at the dome.

 

Well, hopefully this info helps others. Czar, thank you for brainstorming with me. OldOneEye, thanks for checking in.

[CzarDestructo]

The LED festoon works because LEDs only need the static X volts, usually 2, to sufficently bias it into turing on. After that they're current driven devices. What was happening is your footwell LEDs were eating up a bunch of voltage, I assume all the interal LEDs are in series so roughly 8V. 4V is not nearly enough to sufficently heat up the indandecent coil to the point were it outputs light, however 4V is more than enough to bias an LED.

 

Ok thats enough from Mr.Wizard.

[Gator GT]

Well, Mr Wizard, it is appreciated! Thank you!