licence plate lamps

[torquey]

Hi all,i have fitted new licence plate lamp holders and bulbs and now i have an error come up showing rear lights and licence plate i am not sure if i have the correct bulbs because looking through the bulbs list it shows 5w early 10w late,of course it might not be a bulb issue,the lights are working, the car is an`89 chromie vert,if anyone has an idea what the problem could be i would appreciate your input,Thanks.

[andysheep]

Mine said last night that they were 12v?but mines a facelift cabby

[Phil3201]

Hi
I just fitted LED lights in my 1984 reg plate lights and there you go warning lamp is on. The system expects a min current draw so a lower wattage (tungsten or LED) will reduce the current and make the system think the lamp is blown, bingo warning lamp on. Not sure what current its looking for but the system was happy with 2 x 5W lamps, they are wired in parallel. Ohms tells us P=V x A so each takes about 400ma, total 800ma. I will need to add a parallel shunt resistor to put make the lamp go out, about 15ohms should do it. The downside is that if the LED's do fail the indicator will be useless as the shunt resistor will probably still keep it happy. I will try and find a critical value using a variable resistor when I get time and a suitable resistor.
So we need to ask what is the advantage of LED's in this position if we need to add shunt resistors. My feeling is just clean the lenses and put the 5W tungsten lamps back in

[scallyally]

So we need to ask what is the advantage of LED's in this position if we need to add shunt resistors. My feeling is just clean the lenses and put the 5W tungsten lamps back in[/quote]

Problem solved in one! I fitted LED's to the interior lights, lasted a fortnight!

[Brianmoooore]

First of all, a '89 cab. is 'facelift', whatever bumpers and bodywork it has. It's only the latter items that BMW was slow in updating.
Try a couple of new bulbs from a different source before getting too involved in fault finding.

[ChrisHC]

You need canbus compatible LED bulbs to draw the same current, say from http://www.autobulbsdirect.co.uk/LED-Bulbs-c/ A lot of LED bulbs seem to be complete rubbish unfortunately.

[Phil3201]

Yes you may thinks so, and I fell for it for a second as well but think about it, they are simply LED lamps with current shunts or resistors build in. The overall current drawn is the same as tungsten. the colour is whiter but apart from that, no advantage at all. The standard units are still available they were used on lots of later models. you can use LED lamps if you don't care about the lamp monitor being on, or add a resistor if you do. LED lamps are pennies on fleabay, I just bought 10 for $2.50 but as Scallyally points out quality varies.

[Brianmoooore]

The biggest enemy of LED reliability is heat - the actual point where the light is produced is hotter than the surface of the sun, and this heat needs to be dissipated effectively, and failure to do this is why cheap LEDs fail.
Building an extra 5W or 21W heater into the same enclosure as the LED isn't the cleverest of ideas.