Yesterday the bulb failure light on the dashboard of my 1995 A4 2.6 Quattro lit up,I found that both of the rear tail (side) bulbs were not on, changed both bulbs & still same problem,the indicator,reverse, brake,fog bulbs are all working in both rear lamp units.
The tail (side)/brake light bulb is a double filament,2 contact pin bulb,(12v,5/21w) the bulb holder in the lamp unit has a single offset contact pin.When the tail (side) light switch is on,there is approx 6v @ the contact pin,when the brake pedal is pressed there is approx 12 v @ the pin.It would seem that the single contact pin is used on only one filament of the bulb for both side & brake light operation.
When a good single filament bulb is wired to the single contact on both rear lamp units giving 6v for side light operation,the bulb will not light.
When the correct double filament bulb is fitted in either of the rear lamp units,it will not light & the 6v @ the contact pin in the other unit goes down to 0v
I am baffled & would appreciate any advice that any one has.
Thanks Dave
The tail (side)/brake light bulb is a double filament,2 contact pin bulb,(12v,5/21w) the bulb holder in the lamp unit has a single offset contact pin.When the tail (side) light switch is on,there is approx 6v @ the contact pin,when the brake pedal is pressed there is approx 12 v @ the pin.It would seem that the single contact pin is used on only one filament of the bulb for both side & brake light operation.
When a good single filament bulb is wired to the single contact on both rear lamp units giving 6v for side light operation,the bulb will not light.
When the correct double filament bulb is fitted in either of the rear lamp units,it will not light & the 6v @ the contact pin in the other unit goes down to 0v
I am baffled & would appreciate any advice that any one has.
Thanks Dave
