SRS Light Constant ON!
 

Today I was leaving the grocery store, and I noticed my SRS light was on... and it didn't turn off! I stayed in the car for about 5 minutes hoping it would turn off (lesser malfunction when only on for temp time at startup)... so I have a constant SRS light now! Everything else is fine with the car.
I do have one thought though... about 1/3 of the time, when I engage the rear defroster, the light flashes, indicating a low voltage.. it always will come back on (steady) a few moments later. My chargine system seems just fine though... along with my really new MB battery. No other low voltage/no starting symptoms whatsoever. Well I decided to check out my owner's manual, and it said that low voltage could trigger the SRS light.
My question, how low must the voltage go for the SRS system to detect a malfunction? My ABS light is not/nor was on at all. So if this is the case, I'm thinking that the voltage would have to be the min voltage that the ABS needs to function properly.
I hope that made sense.. thanks!

David,
Check your alternator output.When my srs
light started flickering,I found out my alt.
is going south.

How do I check my alternator output? I believe I can check it through the climate control...?
My SRS light is constantly on... no matter what.. no flickering. But maybe my car's computer is different, holding a code and storing it.
Did your ABS light come on in congruence with the SRS light?
THanks. :rolleyes: :o :p :)

I recall something about a blown OVP Relay fuse causing the SRS light to come on. Might want to do a search on this subject.

Brian16V

David,
My ABS did not came on.What I did to
check my alt.is attached a multimeter to the
battery and have my son rev the engine at
about 2500rpm.You should have at least 13 1/2v.
if it stays at 12v.your not charging.In my case
thats what happened.New alternator.
Good Luck!

Dave, if system voltage drops below a certain point for a certain amount of time, the SRS will disable. I can't recall the voltage, but anything below 11 or 12 volts would be about right. Check the alternator output with a volt meter. Cigar lighter socket is an OK source inside the car. Test with no load at idle, record reading, put a load on (headlights, fan, rear defrost, etc). Bring the RPM's up to about 1500. If you're not getting at least 13 volts, I'd suspect the voltage regulator. A new battery would mask the decrease in charging capacity initially. If you drive a lot at night, it won't for long, but daytime driving is less stressful on the electrical system. Good Luck.

If your battery hasn't quit on you by this posting you can safely assume that the charging system is working correctly. A battery that is not being charged or charged properly will simply not stay charged for very long.
The most common cause of the SRS light in W202 is one of the front seat belt buckles going bad. Retrieve the code and replace the suspect buckle if necessary. ;)

Yeah, charging system seems just fine. Car starts right up every time. I will still check the voltage.
I already had an instance with the front seat belt buckle, with resulted in changing one of them... it's possible the other buckle could be faulty, but the SRS light would go out after a minute or two, it is now CONSTANTLY on, disabling the entire SRS system.
I was thinking though... the night before the SRS light went on, I replaced the door pin switch in my driver's door, removing the interior panelling on the B-pillar... the ETR is in there... maybe I did something with that... but then why did it come on quite some time later...
I'll just have to have the code checked...
Thanks a bunch.
Happy New Year! :eek: :D What a crazy night.....!!!!!!!!!!!!!! ;)