ml320x5

Wondering if anyone have a solution or come across for this situation.

Third brake light works good when key is at ON position but no engine start. As soon as the engine is running, 3rd brake come on for a split second and stay off.

A1EK

Try looking at the connections behind the lining, they may have slight verdigris corrosion causing a loose contact.

P.S you access the brake light from inside, there is a bracket that holds it in place with 2 nuts.

ml320x5

Thanks for your suggestion. I checked and it was ok.

I am sure the connection at the light assembly is good cause as I said, 3rd brake light lighted up when key at on position (engine not running). I can manually turn on all the brake lights within SDS. So that tells me all wirings are making good connection.

ml320x5

Problem was current fluctuation. Funny is the old light works with 12V source hooked directly to it and also works in car with key on but not engine start. As soon as engine running, SAM killed it. Must be something with the leds or housing assy. Thanks Rudeney gave suggestion on other forum.

Put a new led assy and it works.

Gene Fiorot

Voltage when battery in charging exceeds 13v the Leds ability to light. Faulty Resistors , etc My guess

ml320x5

What gets me is the light lighted up with external 12V, lighted up with key on but no engine running. All Leds within work prefectly, not a signaled burned bulb. No visually defect. But as long as engine runs, that little resistance, voltage spikes trip the SAM cuases it to failed.

I am glad there're more aftermarket parts show up for R230. I've seen a single unit cost $2~300. I will save my $$ for other repairs/maintence..etc.