jurisals

Hello everyone, I have recently purchased a Mercedes Benz 190d with a 2.0l engine. I got it for a real bargain - 300eur and it came with a lot of spare parts and a spare engine. As a car of that age and from sitting outside and rotting for a few years, it has many rust holes that I am currently fixing by cutting out the damaged metal and welding in a fresh one. I must have left the battery connected at one time when I was welding, and now there are many electrical problems. The dash doesn't light up, and I hear one relay underneath the driver side panel constantly clicking(even with the key out) The horn also doesn't work. The engine cranks. Could anyone have any information they can share to help me in this situation? It is hard to find information about the electronics of these cars. I heard something about a high-voltage thing, that comes with a fuse. Any information would be really helpful. Thanks!

dolucasi

Sorry to hear about your problems on the newly acquired car. I do not know about the diesels but the gasoline cars are all a 12V system, nothing high voltage, with the exception of ignition of course.
And in the diesel you do not have ignition, so you should not have any high voltage electronics.

Is your welding tool a high current electric welder? Is it possible to fry electronics with that? I suppose just removing the battery +12 would have solved that problem as you say.

Sure sounds like you may have fried some electrical parts. You should be able to find representative circuit diagrams for your car on-line. I happen to have a Haynes manual (US) that covers diesels and has some of the circuit diagrams.

From you description some relays are effected/damaged. You may have to go thru all of them by swapping them with a known good relay for each circuit that is effected.

If you can not find the circuit diagrams I might be able to send you pictures from my Haynes manual in the future.

190Efan

There's also a European version of the Haynes manual that's available at www.Haynes.com for about $25.00 and it's well worth the investment. There's also the MB Classic Center who are also very knowledgeable about these cars. I'm glad you're rescuing this particular one as these are great cars when they're well cared for. Mine is gas powered so I'm not familiar with diesels. I do think that all of the W201s used a 12 volt system regardless of the fuel.

jurisals

Thanks for the advices! I just checked the "high voltage thing" I mentioned earlier, and tried to search it on the internet, and what came up was over-voltage protection relay. Could it have anything to do with the problem? When I will have more free time, I will try to find and fix the problem. I am thinking of purchasing the manual you mentioned, it could come in handy with a lot of other things that might come up in the future too. The car would have been sold for parts, but I managed to talk to the previous owner in time and got the car in my hands. The car is in quite rough shape, but I am willing to give it a second chance and save it. I think that the 190e is perfect for learning everything about cars and repairs, as it is relatively simple, and for me as a person who just got their license, its a fun project to start and learn with.

dolucasi

You are right about the 190E/D being perfect for learning about cars and maintaining them. Very good hobby cars as well.
The OVP is a critical relay for protecting sensitive electronics from voltage surges (higher then say 16V).
The problems you are having are with basic relays for basic non sensitive circuits.
While you are at it, you should check the OVP relay fuses to see if that is also fried in the process of the welding.
Some of the relays in the car are the same part number and can be interchanged/swapped for one another. You can start by swapping those around to see if your problem is moving with the relays.
At least you do not have to spend money on those relays until you decide they are indeed fried.

190Efan

I think you should try Dolucassi's suggestion first to try to further isolate the electrical issues. It might well wind up being that the OVP got fried but it's best to try the easy, no cost possibilities first before you spend money to replace the OVP. You don't want to throw needless money away. This is also a good lesson to be sure you've disconnected the battery before starting any work on your car. It's to protect the car as well as your own safety. It's also best to have a manual to help guide you as you're learning so I think the sooner you order the Haynes manual, the better. A good project for you to take on. I'm glad you talked the previous owner into selling you the car rather than having it wind up in a junk yard. Keep us posted on your progress and don't hesitate to continue to ask questions. We're here to help you.