W124 Is there a simple way to deactivate ABS lamp?
 

The ABS light on my W124 comes on intermittently...most of the time it's on. When I asked my mechanic about it, he said fixing it would be more involved than simply cleaning the sensors....and as I didn't want to throw significant money at it, I left it alone. For now, black tape covers the lamp.

It's up for state inspection soon. I'm happy to live without ABS on this car. Is there something simply I can do that just takes the system offline so that the lamp won't illuminate?

I swapped out the OVP relay a while back. I should probably also swap out the ABS relays since it's easy and cheap.

Years ago I bought a 300SDL from a guy who somehow deleted ABS...but I forget how he did it.

Thanks.

If they are doing their jobs the inspector is going to turn the key to the first piston and see if all of the lights including the ABS light come on. so that circuit needs to be intact.

For their rest of it someone needs to study the wiring diagrams and actually understand how it works.

I have other cars. If it was me, I would put the Mercedes on non-op which is exactly what my Merced's is on right now and fix it right later.

At some point in time everyone's Mercedes may get too expensive to fix.

You could read the flash codes I just can't recall which pin maybe 8?

It may not be necessary to pass inspection. You might want to try first. You can just pop the light out of the instrument cluster. As far as I know in NY state you can still pass inspection with abs light on.

In RI and ABS light that stays on fails the car.

Usually, when the 124 abs ligjt comes on, there is an alternator issue...
What is the battery voltage?
Is there any AC voltage read at battery terminals with engine on?

Remove the ABS warning light bulb in the instrument cluster.

13.8v at idle...only consumer on is the aux fan. Then, just sitting there idling, ABS light comes on at 2.5 minute mark.

The ABS module doesn't have blink codes :(

If the light comes on when you turn the key on, goes out once the engine is running, then comes on after you drive for a bit it's likely a bad sensor or bad tone ring on the front wheels.

A simple test you could do would be to lift the front of the car, and using a volt meter on AC, spin the wheel by hand and measure the voltage created. If one wheel is lower than the other you know where to look.

-J

Where would I measure the voltage?

Current plan is to eliminate control module and relays as variables...then investigate sensors.

Measure the voltage from the output of the sensors. The easy place to do this is at each sensor connection, it's a round coaxial connector. You could also measure at the pins of the abs computer, but that is more fiddly.

When specifically does the light come on? That's a major clue in what the computer is upset about.

-J

Comes on about 2.5 minutes after starting the car...whether driving or idling in the driveway. The fact that it does it without any wheel rotation makes me suspect something other than the sensors.

Have you visually inspected wheel speed sensors?

Not yet. I'm going to wait until I eliminate control module and relays as variables.

Here's another option that I used to pass a safety once. Back then I built the circuit, but now you can buy a variety of cheap DC timer modules online for $10 or less.

Wire the light to a "one-shot" timer that is powered by a wire that is hot in On. This will turn the light on for a single pulse, then it will go off and stay off.
Edit: if you can't find a timer with the feature, a "one-shot" can also be made from the normally closed contact of an on-delay relay. Power goes to both the timer trigger and the normally closed contact. When the timer expires, the contact opens, and the light goes out.

Nobody will ever know.