1993 300E 2.8L gas engine won't shut off
 

I recently purchased a 1993 300E 2.8L. The car started right up, however, something was draining the battery and causing it to be dead overnight. I attempted to find the short by removing fuses from the fuse box under hood, one by one, and then testing for current draw at the battery. I checked all the fuses and found nothing wrong, but still had a draw at the battery. Then the car stopped starting. It would just turn over but not fire. I did some research on this site, and since my abs light stayed on constantly, I fiqured the OVP was the culprit. I got another OVP, Part # 201 540 32 45, put it in and the car started right up. The abs light still stayed on, but the car started, however, now it won't shut off with the key. To shut it off, I must pull the fuse from the OVP. Does the OVP control shut off? Should I have purchased an updated OVP with the two fuses, if so, what would be the part #? I suspect that the ignition switch may be bad but I wanted to confirm that the OVP isn't still bad before I rip out the dash to change the ignition switch. Anyone have any suggestions or should I just install a new ignition switch?

1993 300E 2.8L gas engine won't shut off UPDATE
 

I found out today that when I turn the key to the off position, even though the engine doesn't shut off, all power to the windows, blower, sunroof, and radio is shut off. I would think that if the other power is being turn off, the engine should also be turning off and therefore the ignition switch is working and maybe something else is preventing the engine from shutting off. Is this possible? Does anyone out there have any input?

Most people have upgraded to the red top ovp. Just trying to help brainstorm... I checked my 190e wiring diagrams and it looks like two red/yellow wires come out of it (ignition switch). One goes to power distribution and the other to accessories.

Sounds like the ovp is still getting power when it shouldn't?

Edit: two wires come out of the ignition switch

Also if you do get a red top ovp only get it from a reputable source and ensure it isn't the Uro brand.

Try unplugging the alternator, if that works the alternator is fried.

Thanks liquiddog,
I seem to think that I got a bad OVP also. The car started and shutoff fine before the OVP went out completely and the car wouldn't start. I know for sure the old OVP was bad since I opened it up and found one of the relays burnt. It doesn't make sense to me that if the ignition switch worked fine with the old OVP(before the relay fried) and I put in another OVP and the car won't shut off, that the ignition switch suddenly became bad. I have no problem changing the ignition switch, however, I do not want to rip out the dash and change the ignition switch and then still have the problem. I am going to get one of the updated OVP's first and if it doesn't solve the problem then I will change the ignition switch. I appreciate your response to my thread and I will post the outcome. Is a KAE OVP from Pelican Parts a good choice? Thanks again for your assistance, it is appreciated.

Only use original OVP.

This.

If the alternator is is back feeding, the car will not shut off.

I once made the mistake of hooking up a 87 alternator to a 93 M104 system, it was fun finding out why the engine wouldn't shut down.

The one I got was Kaehler (KAE) and I believe it to be OEM. Maybe somebody who has purchased one from the dealer can chime in on the branding. I haven't had a problem with mine.

I've seen them made by two companies, one in Austria and one in some east of the curtain company. The one from the east seems to last much longer.

I'd definitely test the alternator as others have suggested before putting a brand new ovp on. Technically the fuses should blow if something is pushing in too much voltage when it shouldn't, but...

Thanks guys, I will try to disconnect the alternator later today and see if that shuts it off. I will post the results. Thanks again, you guys are great!

Hi Guys: liquiddog, daddi, Edward Wyatt. I disconnected the alternator earlier today, the car started up but still won't shut off. My game plan is to get a new OVP and if that doesn't work then I'll rip out the dash and install a new ignition switch. Do you guys know a reputable place to get a dual fuse OVP at a reasonable price? I see that Pelican Parts has a KAE Brand OVP for $55.25, but I don't think it is a dual fuse OVP. I am going to be away later this week, so I don't know how soon I will get the new OVP installed, however, I would still like to order one ASAP. I will post the results once it is installed. Thank you all very much for spending your time to help me.

Did the car come with the two fuse OVP? To the best of my knowledge your car should have an OVP with a white top and one fuse. Inserting the wrong OVP can cause all sorts of mess.

The one pelican has is the right one. I had my mind stuck in 2.6 190e world, but if you search 1993 300E 2.8 it is white in color.

The car came with a one fuse(10 amp) OVP, Part # 201 540 32 45, however, I thought the dual fuse OVP was some kind of updated OVP from MB. I guess I am just confused since I read every thread I could find on the OVP. Is the KAE OVP from Pelican Parts a viable choice for $55.25? If not, where is a good place to get one and exactly which one am I looking for?
Thanks for all your help.

My bad liquiddog, somehow I missed your post and posted another question about the OVP. I am done asking questions and I will order the OVP from Pelican and I will post the results when it is installed. Someday I hope to be able to help other MB owners with questions, like you guys do, however, I still have alot to learn about these cars....A whole lot:)

Hello liquiddog, daddi, Edward Wyatt,
Once again, thank you guys for all your help. Sorry for the delayed input. I put the new OVP relay in and the car started and shut off.The OVP relay does control the shutting off of the car. However, since I put the new relay in, and the car started and shut off fine, I decided to take it for a road test. About two miles down the road it shut down. No power at all. Engine shut off, no power windows, no horn. Battery drained. Walked two miles home, got another battery and ride, car started fine and I drove it home. When I got home the alternator was smoking and very hot to the touch. Alternator Fried !!!! I'll update when that problem is solved.

That is a bad voltage regulator, which in turn also caused your OVP to fail, this is usually tied with one of the diodes in the diode bridge thinking its a two lane highway.