Hello all:
I have a 1993 300TE with the 3.2L engine and the ABS light is on constantly. I have pulled the overvoltage protection relay out of it's socket next to the battery and when I shake it, I can hear a rattling sound inside the relay. After doing some research I found a statement on another Mercedes-Benz forum that if the OVP relay rattles like this it is no good and should be replaced. Can anyone here confirm that?

Thanks
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Steve

Well just pull it open and take a good look inside for the part making the noise .Look for burns to the board and re solder all the joints .

what battery voltage do you have when running?

If you open it up, you'll likely find that it's toasted. Replace it. Absolutely under no circumstances attempt a repair. If a trace has burned, the zener is likely bad, and you won't be able to verify that visually.

So this model of OVP relay has three separate coils inside and today after pulling the relay apart and seeing no issues with burnt traces, I plugged the relay base back in with the fuse installed but no cover in place.

When the ignition key is engaged or the car is started all three of the relay coils are pulling it's respective contact plate down into place.

Is there any other troubleshooting I should be doing to isolate any issues that would cause the ABS light on the dash to stay on all the time?

The Mercedes part number on the outside of the relay is: 000 540 67 45

If that is helpful at all.

the only appearance i look for is the date on the relay. older than 8 years old, replace it. get a dealer relay, those in th aftermarket cause problems when new. replaced alot over the years and fixed a few abs lights like that.

After receiving complaints (hat tip to Mr. O'Brien on BW for his detailed feedback), in 2018 we made several design changes to URO Overload Protection Relay 201 540 3745. We made the circuit board traces wider to handle heat better, and added plastic insulators to prevent PCB to metal case shorts.

In fact, if you check verified buyer reviews on that big "jungle" online retailer, we received nothing but 5-star reviews in 2019 and 2020 for our updated version of OVP relay 2015403745 !

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check ABS relay under ABS pump cover