W124 ABS dash-light start-up sequence
 

After starting our 1988 W124 300TE, the ABS dash-light came on.

After re-starting the car, all is well, and the ABS functions as well.

When starting the car, but before engaging the starter, I was under the impression that some dash-lights (e.g., ABS, SRS, etc.) would illuminate for about 1-second then go out.

The SRS light does this sequence, but the ABS light just blinks very quickly, then goes out, not waiting 1-second.

Is this normal?

I'm asking because I read that the ABS unit will "shut-down" if the voltage is less than 10.25 volts (my voltage is above 12.5).

BTW: I did check the Over-Voltage-Relay's fuse (it was OK), and I swapped out ABS control-units (I have a spare) but still get the quick "blink" sequence instead of the 1-second wait like SRS.

:-) neil

Did some research in the W124 Service CD-ROM.

Read up on section: 42-0720 Brakes: ABS: Electric Test Program.

Pulled the ABS solenoid valve relay (42-0710) (silver-colored "ice-cube" relay) and tested contacts 30 & 30C for a faulty diode.

Sure enough, bad diode, got a new relay for $33, and all is fine (MB pn# 001.542.6719).

I will try and open up the bad relay and install a new diode. . .

BTW: this relay is DIFFERENT than the other "ice-cube" silver relays which do NOT have a diode between contacts 30 & 30C.


:-) neil
1988 360TE AMG
1993 500E

Neil,
Where is this ABS relay located?
Thanks

Under the black plastic cover of the ABS pump, at least for my 1988 300TE.

:-) neil

Thanks Neil. I'll check to see if its the same on my 91 300e. I know the other silver cube relays are with the rest of the relays behind the fuse box.
Rich

It should be the same.

If you hook-up an OHM-meter to terminals 30 & 30C of the silver-relay, and measure continuity/0-resistance in both directions, then the diode has gone bad.

:-) neil

I know this is a very old thread, but I have the identical symptoms on a 1992 400E. I pulled the relay in the ABS unit and it looks like the diode is OK - measured .554 on the fluke diode test. What led you to that relay in the diagnosis? I have not been able to do a real diagnosis at this point. Just things it "could" be, like this relay (may get one as a precaution), ignition switch, alternator....

paul