BrabusBenz300E

I needed a jumpstart after my 124 sat for a 7 months, never to be started (bad idea). My friend decided to "help" by hooking up the cables backwards. He's an accountant, so for him black always means positive and reg always means negative Casing on battery cable started melting, smoke ensued.

After it all cooled off I found my battery was shot, but the car started right up when I put a new battery in.

Now for the question...

Lots of warning lights are on now as a result of the debacle. What broke as a result of hooking up the cables to the wrong terminals? Did some sort of fuse or relay blow up? I don't know anything about electric of wiring in any cars.

Thanks for the help.

rivcal4life

Search ovp and you may find your solution.

ps2cho

This is why there was a bulletin that 124's should NOT be jumpstarted for any reason. Remove the battery, charge it outside the car then put it back in is the correct procedure. I would start with your OVP as the likelihood it is toast is high.

Goodluck!

BrabusBenz300E

Update: the alternator isn't charging the battery, battery dead after running for about 15 minutes.

Replaced the battery cable as it was fried, didn't fix it. There's gotta be a short in there somewhere. I really hope it didn't fry that alternator.

YNVDIZW124

Go to a junk yard and buy a used one for $15. If that doesn't work buy a new one for like $80.

rivcal4life

Did you check the OVP (Overvoltage Protection Relay)

I believe they are known for causing issues with recharging.

BrabusBenz300E

Is replacing the OVP the only way to check if it's bad? The car runs beautifully, for the record, battery not charging the only main issue.

BrabusBenz300E

http://www.benzworld.org/forums/r129...-gone-bad.html

Looks like someone else did the same thing on an R129. Is the OVP in the same location on a C124, behind the battery?

I'll start by replacing the 10A fuse in the OVP.

ps2cho

You blew your alternator. I'm sure of it now. Check voltage when the car is running. If it is less than 14v you need a new one. If it is dead you should see your voltage keep dropping because it is not charging the battery.
I remember this happened to my wagon 2 years ago about 3 days before I went to the car and the battery was dead and I got stranded. Was obvious when I put in a new battery and it still drained after 3 days.

BrabusBenz300E

Sequence of events:

1. Cables hooked up incorrectly on both ends (I believe)
2. BMW started
3. Smoke, fire, etc in Mercedes - Mercedes key never turned on
4. swearing

So it fried the alternator without even turning the key on?

ps2cho

Well...

A) All your dash warning lights are on -- Indication of alternator not functioning
B) Your battery keeps discharging
C) You have replaced the battery

It points directly at the alternator.

Like I said, check the voltage when the car is running and post up the results
Next, check out the voltage regulator. It is attached to the back of the alternator by 2 bolts. 2mins and it will be in your hand. Check for any bad signs...otherwise I'd look into the alternator.

neanderthal

Alternator.

BrabusBenz300E

Confirmed it's the alternator.

Worst of all, I'm selling the car to a friend (different one than the one who was contributorily negligent) for a good deal already. Sigh

BrabusBenz300E

Where is the OVP located on a C124?

Replaced the alternator, fixed the battery discharging issue.

Current symptoms: ASR & ABS light illuminated, and now I noticed stereo isn't getting power.

Does this sound like OVP? Blown fuse for the stereo? Thanks again guys.

BJaltima

You likely fried more than your alternator and ovp.....

My friend did the same in his Jetta, fried all his electricals, A couple thousand later and his car never was the same.

Electrons can be pretty nasty :p

Good luck.

BrabusBenz300E

^ I hope it's not more...

but can anyone tell me where the OVP is?

BrabusBenz300E

Can someone tell me where the OVP is? Do you think it's the source of my stereo not working? Are there fuses that could have blown for the stereo? If so, where are they?

ZorroAMG

OVP is behind the battery under the thin black plastic sheild.....It's a silver with a red fuse on the top.

ps2cho

The OVP has nothing to do with the stereo. It only powers some of the KE-Jetronic controls. Your stereo is a completely different thing. Check all fuses first in the fuse box, then if it an aftermarket stereo pull it out and check the fuse (which is usually in the device itself, or on the power lead).

BJaltima

BrabusBenz300E

k.

Thanks for the help everyone. Car is no longer mine but I promise the buyer (my ex ) that I'd at least replace the OVP and get the stereo working. Hopefully OVP gets the lights and the stereo is just fuses, hopefully.

What fuse in the fuse box controls the stereo? Or is it just the one that is in behind the dash as mentioned above?

ps2cho

There should be a sheet that tells you everything inside the fuse box.