Radio and Wiper Circuits Drop at Same Time
 

I’m currently dealing with a very strange electrical circuit dropout issue. Here is the behavior. The car will randomly lose both the radio/cigarette lighter circuit and the windshield wiper circuit at the same time – never separate. Here are some observations that go with the circuit drops:

• No fuses blow
• Seems to happen more frequently when the car is really hot – as in summertime but it does happen in winter – just not as often.
• When I turn off the car and start back up, the circuits sometimes come back on but not all the time.
• Occasionally the push of a climate control button will coincidentally have the circuits come back up but again not all the time.
• I do have a Kenwood cd player installed in place of the original radio. Didn’t have any problems after it was installed just down the road. It’s not a very powerful radio so I don’t think it’s pulling a lot of power.
• In the fusebox, I do see that these circuits #4 – radio and #6 wiper are side by side and connected in the fuse box by a metal strip. I notice that other circuits are grouped similarly.
• At this point, I don’t have a circuit diagram but will be looking for a good source.

Would a good start be to just clean all the contacts and replace the fuses on both? I wouldn’t think losing one fuse should shut down both circuits but who knows. I have read that these fuses can be culprits even if they look fine.

We always hope that someone will read this and say – yep had the same problem and it is x. Not sure this will be that simple but anyway – here is a start. In searching, I really didn’t see anything very close to this issue.

Thanks!
Gib

With the car running, jiggle your ignition switch and observe what happens. If electrical components shut off, then you need to replace your ignition switch. Doing this solved a recent electrical problem in my SD where the ACC and blower would cut out intermittently. All the power for your electronics routes through the ignition switch. Once the contacts wear out, you can lose power to various things.

The only point in common for both these circuits (4 and 6) is that they share the same set of contacts in the key switch.

Diagram available at startekinfo.com, select workshop resources on the left, page through to 123 Service Info.

I would look at replacing the electrical part of your key switch. This can be done separately than the lock portion. Be sure to disconnect the battery, the key is directly fed from the battery and then on to the fuses! The procedure is located at the above location or search the forum.

I believe you both have diagnosed the problem! I took the car out last night and the circuits promptly dropped. I gave a slight wiggle to the key and they immediately came back up. They probably dropped a total of 5 times over the evening and each time the key movement corrected it.

I will proceed with the replacement of the switch. I did replace the keylock probably 3 years ago. Looks like there is a lot of documentation out there on the replacement of that part but I'm glad you verified that the electronic part can be done separately.

Also Eatont9999, this was very opportune that you posted. I've got my ************** kit to replace the injector nozzles and that is on the todo list. Your videos will be a big help.

Thank you both for the excellent guidance! I'll update once I have the ignition switch replaced.

Gib

I am glad to be a help. Let us know how everything goes!

You will have to go through what you did to replace the keylock (Lock tumbler), and you need to be in position #2 with the bent paper clip, to remove the Ignition Switch plug.

(Is it #1 or #2 position? been a while)

You will have to remove the Steering Lock assy. to get to the 3 screws on the rear of the switch.

1983 Mercedes-Benz 300D Base Sedan - Ignition - Page 1

I have read the screws can be accessed, but don`t see how you can get to them.


Charlie

Here is the update:

I purchased a Beck Arnley switch and went to install today. I did end up removing the entire steering lock housing.

My problem happened when I went to test it by turning the key. The key was tougher to turn and it really didn’t release well from the start position. I pulled the switch back off and think the problem was with the cheap ignition switch. I took the switch back off and plastic pieces fell out including one of the main plastic supports where the screw passes through. Also, a couple of tabs that click into the housing broke off.

So I’m off to order another. Charlie, thanks for the link to the parts. I had already ordered this one prior to your post.

Will update later when we do the sequel.

Thanks!
Gib

Get a switch from this site or another that specializes in MB parts. Local auto parts shops will carry mostly crap parts. I don't think there are any Beck/Arnley parts that you want to install in your car. I think Valeo made the lock and switch assembly in my car. Worked fine the first time.

I did see the Valeo steering lock/ignition switch when I was parts searching. I was thinking while I have it all apart, it might be worth it to just go ahead and swap the whole unit. Good to know you've had good luck with that brand.

Thanks again - I'll report back!
Gib

Did you get the new ignition switch and lock yet? Just wondering how things are progressing.

A few tips, while they are fresh in my mind. I used a jeweler's flat head screwdriver and GENTLY tapped it with a small ball-peen hammer to get the lock collar off. Made of hardened steel, it was the only thing I had at hand that would fit in the hole and be sturdy enough. I also soaked my ignition lock cylinder in ATF while working the key though it to clean out the 32 years of dirt and grime. Blow out the cylinder of excess ATF with light shop air. Be careful not to use too much pressure and blow out the tumbler pins.

Actually working on it now. Got the steering lock/switch Friday and trying to install now. Is there some trick removing the contact switch from the old steering lock? I've tried turning the key to different positions thinking it might release but so far no luck.

Thanks!!

It's a PITA. I broke one of the tabs on mine. Try a flat bade screw drive and hammer it out but gently.

Well we have success!

First off, I got the contact switch off and luckily it was intact. The trick for me was to use an 18 gauge brad nail from my nail gun. That was thin but sturdy enough to work in-between the switch button and the steering lock housing. The nail slid in and once I could see the button completely depressed, the switch slid out. Let me add that you do need your keylock in and the key turned to position 1.

Got the new lock installed and the only lingering weird behavior is the wiper blades bump up about 1/3 up the windshield when I turn the car off and then do one cycle when I turn it on. There are some posts out there mentioning this but didn't find anything definitive. We'll see if that continues.

For the moment though - thanks for all the help! Injector nozzle replacement will be the next project coming soon.

Glad to hear you got most of the issues resolved!

I have a wiper problem in one of my cars, too. Similar symptoms as yours but random and sometimes they don't shut off or come on when the blower relay changes fan speed. I have been looking for years but still can't find the culprit.

Well I had numerous trips out yesterday and the wiper bump seems to have gone away. Hopefully that one corrected itself.