Reset warning lights after battery replacement (W124)
 

Hey all,

My Interstate battery from ~12 years ago finally died in my '95 E420. Have replaced with a battery now, but all instrument cluster warning lights are on. Is there a straightforward DIY for resetting these?

Thanks!
- Ryan

Replace the regulator in the alternator.

No reset on w124 .
Only radio code . Did you fix all the wires on in the right place?
Did the engine crank ? Need more information to help you .

It sounds like, alternator quit charging and depleted the battery. New battery was installed but alternator issue was not addressed.

On some cars ( especially 80's Japanese cars ) the alternator charge light is tied into other dash lights to provide a key on, engine off bulb test.

This is an example of why diagnosis is key before changing parts.

Battery was diagnosed by finally failing to turn over and start the car - confirmed by my indie shop. Charging system overall was deemed ok, so I opted to save a couple hundred bones by buying and replacing the battery myself. Car fires right up now, just have the warning lights on now

Evidently there's more to it (being a nearly 30 year-old car doesn't surprise me that a couple links in the chain may have failed at once).

On my previous W124 300e, there were 3 causes for the cluster warning lights:
-charging (voltage regulator / alternator)
-OVP (Over Voltage Protective relay)
-battery

All the warning lights feed the alternator as part of the flashing circuit. If the alternator is not charging, they will remain on after the engine starts. OVP will affect ABS and tach, but not all warning lights.

Did they try to recharge then load test the battery?

Saying the battery is bad because the engine won't crank is like saying the gas tank needs replaced because there isn't any fuel getting to the engine.

RE: A car battery is like a gas tank, if run low it must be refilled. The alternator accomplishes this task while the the engine is running. Car batteries are not like single use flash light batteries.

Did they put a volt meter on the battery with the car running and old battery? What was the voltage?

The shop wanted $ 200 USD labor to change the battery?

Have you tested the charging voltage with the new battery?

I would change the voltage regulator . Also in the console you have bulbs that light up the dials ,, the row of bulbs on the bottom have to tell you all is working right . Can you see the charging light bulb as you switch on the key ?. without starting the engine .No charging light,, then its just a bulb replacment you need to do . If the bulb for the charging sequence is not iluminated it breakes the charge up citcuit . . And without the bulb in place battery will go flat .

Not true at all. The rest of the lights that light up feed through diodes as a "backup" in case that bulb burns out. The only thing that turns them off is the alternator begins charging and their potential to ground disappears when it does.