1987 300E Electrical Gremlin

My 1987 300E suddenly developed some sort of sporadic loose or poor electrical connection somewhere.
A week ago the radio (Blaupunkt replacement) suddenly went dead, no
lights at all on radio panel. It then would come back on and the antenna would re-raise. It happened briefly the first day, then went dead for a longer period of time, then would suddenly come back on. Examined the fusebox connections and replaced radio fuse with new red one with no change.
Yesterday it went dead and I reached up to switch the sunroof up and found it was dead too, although I could hear a light growling like the motor was trying to do something. When the radio was playing, I used the sunroof switch the radio went dead then came back on when I released the sunroof switch.
Car starts fine and runs great. Headlights, turn signals, brake lights work fine. Interior lights all bright and dashboard instruments work fine.
Today it was raining and with the radio and sunroof dead, the windshield wipers were also dead. The power windows were dead too although their lights were on in the console. Several miles into my trip all came back on. Radio blaring, windshield wiper came on, windows worked, sunroof worked. Stopped car and hour later when I came out to drive home radio, wipers, sunroof dead, but windows worked this time. I opened the glovebox door and the light was dim orange so slight voltage is flowing. I can push the display light on the radio and it lights up with time but won't play radio or CD and goes back dead after a second or two. Starting or stopping hard do not seem to trigger it. Seems to be just not flowing full 12 volts to the radio, sunroof and wipers systems.
Got home, shut off car, then turned ignition back on and everything working fine and glovebox light now bright.
Where do I start looking?!!
Pete Cowper California
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well, 2 things:
1. Do you have lots of keys hanging off your keychain? If so, 20 years of jiggling can cause the ignition switch to be loose, and the 12V ACC supply to be intermittent. Try it again, using the key seperately/
2. If you haven't changed the fuses, just change the whole lot. They may look good, but the end-caps go high-resistance.
HTH, ws
Pete Cowper wrote:

--
change to leews to mail

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ditto on the fuse... change them all.
As for the ignition switch, that is possible too... to test this try turning your key back a bit more without shutting engine off... does that help? If yes, then your ignition switch is bad.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
After you've changed ALL the fuses and cleaned the electrical contacts in the fuxebox (where the fuses touch, with an eraser) then clean the grounds. I've never worked on a 124 but there are probably two. One from the engine block and a another one, uh, someplace.
Then remove and clean to within an inch of their lives the battery terminals. Do the -'ve terminal first.
This alone may make the problem go away.
If not what's the last thing you added or changed that had a wire atached to it?
--
Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The problem went away on my drive from Visalia to Livermore last Friday (184 miles) and did not return until about 50 miles from home when the radio went dead (along with glove box light, sunroof, tear window defogger, gas guage red light are things I am aware of being dead). About 15 miles further at 65 mph everything came back on including red light next to the needle resting close to empty which had not been on 15 miles earlier as I tried to stretch my tank to home.
Since the glovebox light was still glowing very dim orange, non-moving sunroof still making low motor growl and the radio display button brought the radio lights back on for a second or two before going back out...I am thinking bad ground, not bad wire with a short.
Everything worked fine going to and from work today.
I have already replaced the radio fuse and cleaned all the other fuses and contacts.
I appears to be just a few circuits. Gauges, HVAC, interior and exterior lights all work fine.
Is there a common ground near the radio that feeds these accessories? The multi-page spread out MB wiring diagram really does not show what wiring is together in the car.
Pete Cowper 1987 300E
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I am thinking it is possible that your overload relay is bad.
Ground problem is a possibility at the battery or the battery cable... check that.
Interior grounds are well protected inside the car so it is not likely to get rusted.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.