Re: Light out indicator
Originally Posted by
onehundred80
The 'N' module senses the bulb out condition.
From a MB site
'That was the cheap one. Far more expensive is replacement of the bulb warning module (it is not a relay). It is the largest item in the fuse box and is part number 126 542 01 32. Most if not all, W126 and W124 cars and perhaps others, use this same module. See if you can borrow one just to try it before you spend $$$ on a replacement. MSRP is $210. They are available aftermarket new and rebuilt for less.'
Wow, they used to do that with relays? To monitor bulb current it's simple ohms law, voltage drop across a known resistance when the bulb is good and when the voltage goes away light a light on the dash is the theory but how MB accomplished it in the Crossfire, Hmmm....
Now to monitor excess current you gotta add some stuff...
From the picture below, the in and out would be to and from the bulb circuit on the car. The Rsens is the known value for the known bulb. The analog out would be to the cars computer programmed to monitor a range of X, outside range X would light the bulb out indicator. Yes, you can deduce from this if you wanted a ton of work to do you could change the value of Rsens for the LED's installed on your car and successfully monitor non CANbus compliant LED's. In doing so you would be locked in to the one LED brand and style of course. CANbus compliant LED's have a parallel resister in them to fool the car into thinking the correct bulb is out there by drawing the same amount of current as an incandescent bulb.
http://openenergymonitor.org/emon/si...rrentSense.jpg
Last edited by KDW4Him; May 30, 2015 at 10:29 AM.