The "exterior light problem" is illuminated when i put the parking, and headlights on. I checked to see if any of the bulbs are burnt out--all are fine. The headlights, sidemarkers, taillights work fine, even when i depress the brake. When i shut the lights off, the "exterior light problem" indicator goes away as normal. Again, this light only comes on when i have the parking, and headlights on.

Agron
1989 300E

I've been through this before. Look harder, I didn't find the problem after several attempts, sometimes the burned out light will be obscure, or intermittent.

Good luck,

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in
Mercedes automobiles

The rear license tag bulbs are sometimes overlooked.
For good measure, just make a check list:
Front parking/side markers.
Rear parking
Rear side markers
Rear license plate.

If all the bulbs lite then you have one or more drawing less power. That happens if you get bulbs of different wattage and/or brand. Oshram a devision of Bosch is a good brand often found in OE installations. Many of the bulb sockets now have the wattage value next to the socket. If not match them side to side and throw out all brass based non rated bulbs.

With proper bulbs small amounts of corrosion can reduce the current flow and turn a 21w brake light into a 18w and the system will notice.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Use OEM bulbs only. The detection circuit senses the series resistance of the entire circuit. If only one bulb is outside of the programmed resistance trip point, the bulb out light will come on. I learned this the hard way after replacing a ton of bulbs before I figured out what the problem was..

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Jeff L
1987 300e
1989 300e
1987 BMW 325

Thanks for the reply guys...


I will check all of the lights, including the plate bulbs first thing in the morning. I did replace the OEM headlight bulbs with illegal diamond blue headlight bulbs (same wattage). I put these illegal blue bulbs on a couple of months ago--never had a problem until now. I will put the OEM bulbs back to see if the "exterior light failue" will go off...once again, thanks, much appreciated

Agron
1989 300E

If everything else fails. Have you try the backup lights? I am not 100% sure the are part of the circuit but, you have to go through backup for driving and to park. Right?
J.Hidalgo

Glad we were able to solve this at the "First Annual Running of the Benzes"...Thanks for coming and it was nice to meet you!

Next time, you need to burn some rubber off at the autocross, though...it's a Blast!!

It was a pleasure to meet both you, and Gary. Im glad we found the little problem....had a great time...next time i'll try to get the rubber on the asphalt...both of you guys pulled in great times...


Agron
1989 300E