This warning light for ABS of 420 SEL stays on all the time. I manage to locate the sensors at the spindle and visually check it. I used brake cleaner to clean the sensors and its casing good. All four sensors was cleaned and inspected, no visible damaged found, ..however, the light remains on. Any advice that you can recommend what else do I need to check. Thanks....

Two things. The overvoltage relay must be good for this to work properly.
You can take apart the connector for the sensors and check them. Check for resistance and do the wiggle test on the wires.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

how to check for bad OVP relay
 

I have a similar problem with my 1993 300CE coupe -- battery went low and I had to jump-start it.

Light stayed on since then... is there a procedure to diagnose this?? Also, WHERE is the OVP relay found ??

Dealer cannot seem to fix it, and are somewhat "clueless" IMO.

Thanks -- Manuel

OVP is under the plastic cover behind the battery. It has a plastic cover on top with a fuse inside. Fuse can blow when jumper leads connected.

thanks !! found and fixed it
 

Looked into it -- turns out blue (15 A) fuse was blown when I did the last jump start.

Replaced fuse, and ABS lamp is no longer ON.

Thanks for the help. I'll post pictures of the W124 OVP later.

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Side question: when I was replacing the black plastic cover, parts of it cracked. I infer it went brittle due to age. I'll replace this later -- any risk in leaving it partly cracked (i.e., it won't keep ALL the water off the relays, etc).

I don't know how much of a breach you have with those cracks, but for now, duct tape the damaged portions until you can get a replacement.

Enough moisture (i.e. driving rain at highway speeds perhaps?) will cause all sorts of running problems. I believe there is a current thread in this forum on just such an incident...

picture of W124 OVP relay
 

picture of my relay below

http://www.imagestation.com/picture/...0/fd6872e3.jpg