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Discussion Starter · #1 ·
Due to the impressive light output of the facelift Omega (non-xenon) headlights, i have fitted relays and Phillips bulbs. Output is now a little better and HID lamps will be the next step i think.
However, the Bulb Failure warning message is now constantly on the screen as i believe that the system does not get a resistance reading from the relays. I believe that if i fit resistor into the line before the relay it should clear but does anyone know what the value could be??
I dont want to go down to my local Maplins and get a shed load of resistors just for fun!
 

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The formula is R = V / I
and as W = V x I
you get R = V x V / W

[where R = resistance; V = voltage; I = current; W = wattage]

Taking V as 13 V (low on charge voltage )
the R value is ~ 170 divided by the wattage of the missing bulb(s)

so

5 W needs 34 ohm (nearest value 33 ohm)
21 W needs 8 ohm (nearest value 8.2 ohm)
55 W needs 3 ohm

The wattage will be the same as the bulb it replaces. Remember they will get very hot so care is required when selecting a location.

Also if there is one common failure circuit for NS and OS bulbs the value will need halving and the wattage doubling (or you could buy two resistors and put them in parallel).

Just a final point, the failure circuits detect no current flow (ie a blown bulb). They may not need to have a full current to think there is a good bulb. The relays will show up as a resistance but far less than than a bulb so it is possible that you can use higher values than I have quoted above.

Did you fit two relays (a NS and an OS) or just use one. If only one it is the unused lamp circuit that is causing the failure to show and you may get away with just one resistor.
 
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