W126 - ABS light on after battery change.

[OneTwoSix]

Hello Folks:

I think I may have done some damage to my lovely '89 560SEL putting a new battery in it and I could use some "where to go from here" advice.

What happened: taking out the old battery, the wrench slipped and contacted from the postive terminal to metal on the car, at the point where the plunger switch is attached to the body. (The switch for the hood light or alarm or something). Sparks flew and I grabbed towel and got the wrench off both parts asap. But there was probably about 5 or six seconds of pretty good continuous contact.

So, get the new battery in, all is well, except the ABS light is on at start and stays on all the time. No other symptoms or problems. Checking through the threads, it seems that the OVP was a likely suspect, so I replaced it. ABS light is still on.

I'm worried, given the proximity of the ABS control module to the point of contact, that I might have blown it. However, are there other relays or anything else I should check before I spend money having my regular shop (Bosch certified) check into it?

And yes, I've checked all the regular ceramic fuses in the box - none blown.

Any help or suggestions will be most appreciated! :-)

Cordially,
OneTwoSix

[stevebfl]

Check the fuse in the OVP relay.

[OneTwoSix]

Originally posted by stevebfl
Check the fuse in the OVP relay.

Mr. Brotherton!

Thank you for your very quick reply! I tried your suggestion, and even though this is a brand new OVP, the possibilty the fuse was bad aready or blew recently is a good suggestion, if I don't say so myself.

So I visually inspected both fuses (I know only one is actually doing anything in this model), they appear fine. I switched them around and the ABS light is still on.

What should I check next?

And thanks again for getting back to me so fast (it's raining out here and having a working ABS system is kind of a nice thing!)

Update: I went ahead and got a new blade fuse for the top of the brand new OVP. ABS light still on. No other symptoms appearing today, though. Going to take it to my shop on Friday and let them diagnose it. I checked the two relays under the ABS cover and they seem to be working. Don't know what else to do, so it's shop time!

Cordially,
OneTwoSix

[OneTwoSix]

Greetings all:

After a full round of diagnostics, it was the ABS control module that got fried. The flow from the battery, as the contact point was so close to the module, fried it instead of being "caught" by the OVP relay or even the ABS relays under the plastic ABS housing cover. At least nothing else got burnt (except for a slight singing sensation in my wallet.)

The new ABS module costs about $1,392.00 new but my shop found a second-hand one for $500.00, still quite an expensive slip on my part.

One last note: in this case, MB is fine with putting in a "used" module as they so rarely ever go bad. Besides that, my shop gives me one year on P&L.

Cordially,
OneTwoSix