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I've had this intermittent problem with my 84 Euro S since purchasing it where the rear running lights stop working. At some point they'll magically start working again. The front running lights work and looking at the fuse diagram, they're separated by side, not by front and rear so if a fuse was blown I'd lise left feint sns left rear together or right front and right rear together, but both fronts work and ive lost both rears.
All the other lights work - turn signals front & rear both sides, fog lights, headlights, hi-beams, front running lights, rear fog light, & brake lights....it's just the two rear running lights. I dont have any side markers on the car, like have been removed vs not that they're present and not working.
I looked at the bulb controller by the parcel shelf and there is zero corrosion on the male pins or female sockets.
Maybe my bulb controller has failed? Any other things to check for both rear lights to go out together and then come back and work again together?
If you pull out the plug from the Bulb Check Control and make a jumper like this then you can quickly determine if the problem is the controller or not (it probably is).
If you pull out the plug from the Bulb Check Control and make a jumper like this then you can quickly determine if the problem is the controller or not (it probably is).
928 Bulb Check Module Plug Jumper
That's a great idea. So which pin # brings power in and which pin number(s) send power to the rear running lights?
For extra clarity, the parking lights on the rear tail lamps are the green jumpers (they are separated into individual power supplies). The brake lamps are powered by the white jumper which takes a common power line in and distributes it into left/right circuits.
For extra clarity, the parking lights on the rear tail lamps are the green jumpers (they are separated into individual power supplies). The brake lamps are powered by the white jumper which takes a common power line in and distributes it into left/right circuits.
So I would just need to recreate the green jumpers and see if the rear parking lights work, and if they do, my bulb controller is bad, correct?
All my other lights work, including the brake lights.
When these controllers fail they fail progressively. Mine would sometimes (~80% of the time) work well enough to light my parking lamps then occasionally pass only 6vdc to the right parking lamp. People were stopping me in traffic telling me that my rear lights were out at night and when I parked somewhere to check, they were back on. Fun times.
Finally one day when I was working on the rear ground, I saw the parking lamps go out and I had a 5 minute window to take some voltage measurement. Sure enough the voltage was very low - too low to illuminate my LED bulbs. Then the lamps came back on!
So, I made those jumpers and now the bulbs are brighter and I don't get the LED bulb errors I was getting. The check control is still in the car but unplugged. I don't miss it; I don't need it.
Oh, so you have these in there permanently and have completely bypassed the bulb controller. If I did that, I could also install led rear running and brake lights...hmmm?
Would the turn signals still fast flash if I were to put led bulbs in those where that hyper flash is controlled by the bulb controller or is it the turn signal relay (I know they make led versions of the relays, but curious).
Yes, my jumpers are a permanent module bypass. The crimp connectors I used were generic 0.157" male bullet connectors available in any auto shop that sells trailer wiring connectors. They fit perfectly. Someone else made a similar item using a 12-pin Mercedes connector from a 70's era Merc.
To fix your hyperflash issue you need to get a LED compatible flasher. I have a SuperBrightLEDs CF13GL-02: 3 Pin Black European Flasher which took care of my hyperflash issues.
All the bulb check control does is detect when a bulb is out on checked circuits and report the condition to the central warning module. If you look at the wiring the amber turn signal lamps don't pass through the check control module; therefore it has nothing to do with flashing or the turn signals.
05-11-2023, 04:33 PM
84 Euro S - No Rear running lights
