ABS Light
 

1988 260E

A couple weeks ago I noticed the ABS light was aglow on my kid's daily driver. Well, I took it for a spin but noticed the light ONLY comes on after it is started AND when the brake pedal was depressed. It will remain on until the key is turned off. Once again, after start up, when the brake pedal is depressed - *POW* - ABS light! I just replaced my OVP with a new one and was hoping upon hope it would remedy it, SRS light, and my "light bulb out" warning light. But no. Any ideas?

The abs system is somewhat basic. Start at the wheel speed sensors and work your way in. There are 3 total. One on each front wheel and one on the rear differential

How would I go about testing them? With multi-meter?

Don't quote me, but I believe they are Hall effect sensors. Trace the wire in to the engine compartment, you will find a plug. There should be a reading of " x" ohms, and when you spin a he wheel that value should fluctuate.

Someone with a service manual can chime in with the specific readings.

If the abs turns on on the first press of the brake pedal I'd be looking for a broken wire, or something a bit more obvious.

I've had this problem with my ABS before too. First, if key is turned on and before the car even starts moving, if the ABS comes on and doesn't go off, check the OVP. IF the car moves and the light comes on check the wiring from the wheel hubs (usually the front) to the plugs in the engine bay near the wheel well. Check for continuity, I forget the values, but unplug the connectors and check resistance on the actual sensor by placing one lead in the center female opening, and the other lead on the part just outside the inner opening, but still within the connector. I think its something like 1.1, at least this is the case of my 201.

Yesterday, I installed a brand new OVP. I was disappointed that the ABS light popped on after starting it up and touching the brake pedal. I took a chance since the old OVP was possibly the original.

If this was my first experience of MB ownership, it's likely I'd never own another. But my other two cars before this (one of which is our DD) are/were exactly the opposite. I couldn't ask for better service from them, but not so much the story with this 260E!

So far several people have ruled out the OVP as the issue and suggested tracing the wiring and finding the root-cause for the fault (the light is telling you there's a problem in the system). So far the OVP has been replaced (even though it was fine), but the wiring hasn't been checked. The car is at least 28 years old and things fail regardless of who owns them and how well they're cared for. How is this the car's fault again?

The matter of quoting is inevitable; but the sensors are not Hall type, they are simply two-wire, magnetic, inductive pickups, aka VR sensors. There should be conductivity through the two wires.
Fronts: .85 - 2.3 Kohms
Rear: .6 - 1.6 Kohms

Well, first of all, I'm not 'blaming' the car! I just simply have a low tolerance for 'stuff' being wrong with my car especially electrical gremlins. I have better things to do with my time.

I've already spent more time than I'll ever recover from reading thread after thread after thread of similar symptoms for glowing lights on the dash panel. Standing by my comment that I would likely not own another MB IF I HADN'T HAD SUCH GOOD FORTUNE WITH TWO PREVIOUSLY ACQUIRED CARS.

Thank you for this info, when I have the time to get into it, I'm sure it will prove useful.

Another thing you should do is pull the sensors from the hubs and clean the tips. Because they are magnetic, they tend to pick up iron filings and metallic debris, which screws up the system.

Correction is due on that one. I was going off the top of my head on a very foggy memory of my abs troubles many years ago.

Bottom line is that you should get some reading of resistance when tested. Likely one of them is very dirty, or an obvious broken wire. Should be pretty easy to track down.

I agree with Diseasel300, you've stated you replaced the OVP which did not help, the next logical step would be to trace the wiring. There is maybe 2ft of wiring each at the front sensors, which is where the problem is likely at. Your long battle with the abs light may have been resolved within 30 mins - 1 hr of actual physical work on your end. If a glowing ABS light frustrates you to the point where you've made the decision to never own another MB again, I'd hate to see you having a rough idle/hard start issue :D. If it turns out one of your sensors is toast, I may have an extra that I could send you (front sensor only).

Ohh gosh, rough idle and hard start issues are what define my hatred of CIS, only had my engine running 100% correctly for 3 weeks before something else failed and the system went haywire.

But I agree, remove the sensors and clean them off, that would be my first step as it's incredibly easy and should be done as regular maintenance.

Thank you for your pleasant reply. (Some here are not so, you know!) I have had my share of those issues also, but mostly resolved - for the moment. :D

I'm so glad it's not just me then! I marvel at the CIS as a concept and curse at it as an application. My SL has been an 18 year long story of "fix one thing, two more break"! This past month was the first time in ownership that it's gone through 2 consecutive tanks of fuel without having to be parked for something going wrong and I hope it decides to stay that way for a while! I certainly don't mind working on it, but good lord, it's sure nice to drive it without worrying about the "next fault".

Seriously though, these older Mercedes vehicles were marvels of engineering when they were built (they still are), but 20-30 year old technology breaks down from age, use, and neglect and requires service. The more electronic gadgets you have, the more likely they are to have issues later in life. It's just part of owning an older car, if you aren't willing to work on it from time to time, pick something newer and Japanese. Or if you're a glutton for punishment and really love electrical infidelity, buy a Ford from the 80s or 90s! Talk about drive you to drinking...

I wonder if any car that was built, lets say 2010 and after, will last as long as these older MBZ.....built in a time when overhead cost was your least concern. I purchased my 201 in 2005 with 174k as a daily driver, it now has 401k. Since then, pretty much everyone that I am in contact with has been through at least 3 cars, some 5, a piece. :D

ABS Light
 

:: UPDATE:: For those who care, I have taken out the front ABS sensors and done a thorough cleaning - which I must say, was much needed! Unfortunately it did not solve this ABS light problem. The cable leading from the passenger side brake up into the fender well was in good condition, however the drivers side is really cracked and quite 'crumbly' looking. The insulation that is. When I did an ohms test on the drivers side sensor I get a .000 reading. Am I to assume this is good? Also, how would I go about testing the 6-pin relay under the black plastic pump cover? Thank you.http://uploads.tapatalk-cdn.com/2016...61bfe1e951.jpghttp://uploads.tapatalk-cdn.com/2016...38212d52c0.jpg

Your driver side is toast. A quick check of the passenger side would confirm that. What's the part number on it?

Peach parts shows it to be 124-540-16-17. I would say that's the MB part # yes?

What would you want for the sensor?

ABS Light
 

Well, don't know what one has to do with there other, but I replaced a burned out third brake light bulb yesterday and the ABS light has stopped coming on when applying the brakes! Both the kids have been out in it since the bulb replacement and both report that the ABS light has not come on. I'll take it [emoji106][emoji41]

:::ARRRGGH:::

This car sure knows how to keep me humble! So it's been almost 2 weeks since I've seen the ABS light and just yesterday I had to drive it. I turned on the headlights and THERE IT WAS, the ABS light aglow! I turned OFF the headlights and the ABS light went off immediately. I actually did this several times and each time the result was exact. What on this green planet might be causing this :confused: Thanks for your ideas...:D

Anybody???

I can't imagine what the headlights have to do with the ABS system to trigger a warning light. The headlights do load the alternator pretty heavily, is it possible that when the lights turn on, the voltage dips in the system too far? Barring that, you may have a wiring fault somewhere behind the dash or in the fuse box (just chased the latter down in the turn signals in my SDL, wasn't fun).

That's a possibility I suppose. I'll take a reading on my multimeter to see how much it does drop with the lights "on". Dear Lord, I do hope it's not a wiring fault!