I've slowly been fixing multiple small niggles with my 1995 E300 Diesel however recently some problems jumped up that didn't make much sense to me.

Tonight I was checking all my exterior lights by turning on my flashers, headlights, and fogs and while I found a couple small bulbs out in the rear, everything else seemed fine. The odd part came when I went to turn the lights off. My interior lights have always worked, and yet now they didn't. When I opened the door the dome light came on, and my (aftermarket) radio was lit, but nothing else was. All the warning lights in the cluster light when the ignition is turned on and the blinkers flash, but the cluster is not illuminated.

I did have a taillight burn out while I was checking everything, but I'm not sure if that was a coincidence or not. I checked the fuses and they were all fine, but while checking things I noticed that when I slightly depressed the brake pedal the headlight buzzer (or something that sounds like it) very briefly sounds.

Another separate problem only occurs when starting the car when it is cold. The glowplug light comes on and goes off like normal, however once started it feels like the engine is missing for 5 or so seconds if I nurse it to about a minute if I leave it alone. If I apply gas and get to about 1000 rpm, it smooths out and runs normally soon after, even at low rpms. I had something similar happen when a couple burned out, but the glowplug light stayed lit for many minutes after starting. The problem stopped after I changed the plugs, but that was about 8 months ago. I haven't done this often, but if seems that if I leave the ignition on for a while, a bit over a minute, it takes a while to start but it does not run rough.

Hopefully some of yall can help me out, and I'd like to say thanks in advance.

Electrical: If you remove the bulbs you just installed, will the problem go away? Sounds like a bad ground, and installing the bulbs has provided a new path to ground that is mucking things up. You could also try changing all the fuses, replacing with new correct copper fuses; that cures many electrical gremlins when the fuses get older.

Rough start - your car is telling you something is wrong. Did you replace ALL the glow plugs, or just the bad plugs? Perhaps the pre-glow relay is no longer providing the after-glow function?

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Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Interior lighting problems in 124s can be frustrating because there are so many potential causes. Bad grounding at one or more places including inside the instrument cluster is one cause. The instrument light rheostat in the cluster is another. The "amplifier" that illuminates dash lamps other than those in the cluster is a third.

Best to re-visit ever place you worked on, to see if you accidentally disturbed something.

Removing, replacing, and changing the bulbs does nothing, but I just purchased some new copper fuses, so I'll try that when they come in. I've pulled the cluster and will try to clean up the rheostat as well as replace the little red fuse back there. Are there any particular grounds I need to check, or just all I can find?

I just replaced the bad plugs, so I guess that's coming back to bite me. Is there any way to check the after-glow of the plugs?

Taillamp assembly grounds are always suspect—the strips of metal used in the assembly are not really attached but simply jammed together. They can loosen and/or rust over the years.

If you temporarily connect a wire to any one glow plug and run the wire into the passenger compartment, you can connect a 12V bulb to the wire and to a convenient ground. The bulb will illuminate whenever the glow plug is getting 12 Volts. That will tell you whether pre-glow and after-glow are working. It also shows you when after-glow ends. I have such a telltale permanently installed in my '95 E300D. WARNING: Don't pinch the wire and cause a short circuit!

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

EDT: there is a ground point behind the instrument cluster I think. Look for a bunch of brown wires (brown is always ground) that connect to the metal frame.

Jeremy: I love it!

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

Thanks, Max! Another point—if the "afterglow" light stays on all the time, you have a warning that the preglow relay is stuck on (quickly burning up the glow plugs).

J.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Great advice regarding the after-glow light, I'll be sure to work on that when I have a chance, thanks.

I checked the tail lights and off the car every bulb works fine, and I cleaned the ground to the car under the passenger light, but when I put them back I noticed the passenger running light doesn't come on with the lights. The brake lights work as they should.

I cleaned the potentiometer in the cluster but haven't reinstalled it yet. I did try the interior lights without the cluster installed, and they still didn't work. I still need to clean the grounds in the dash, behind the cluster.

EDT,

The shaking/missing on start up is quite common on the OM606.910 although not so in the USA. The US didn't get the OM606 until 1995 to which I think the problem may have been rectified.

We have the problem here in Australia (my OM606 dated 1993 production) and I know it's common in the UK. It's valve recession on cylinder 6.

It might not be the same problem but mine does it in colder weather and a leak-down test will prove it. If it is this problem then new valve seats will rectify it.

It only does it when I'm using a thin oil such as 5w/40, if I switch to a thicker oil it stops.

I'm just living with it by giving a bit of throttle (only needs about 1000rpm) and it smooths out so as to not strain the timing chain for too long.

Where abouts are you?

The others seem to have you covered with the electrical gremlin... someone mentioned to go back over what you have touched/pulled apart recently which is where I would start also.

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1995 E300 Diesel

Sorry for the delay, but I just got back in town from a long trip. I was able to pull the grounds from behind the cluster and clean them, and I put in a jumper from each post to another spot on the frame. I made sure to clean off all the paint underneath the ground spots to ensure a good connection. I also replaced all the fuses with new copper ones.

Unfortunately this hasn't fixed anything. My interior lights still do not come on. I have checked everything I touched when I was initially messing with the car, and I've reached another dead end. Thanks for the help

Let's get more specific. In your car, certain things should happen when either front door is opened (key off):
• front dome light MAY illuminate depending on the position of the dome light switch
• seat belt warning flashes in dome light assembly
• both front door puddle lamps illuminate
• both power front seats can be adjusted.

How many of these work in your car?

All of these work when the door is opened.

In your first post you said the interior lights didn't work…so I'm confused.

Sorry, I wasn't clear earlier. The interior backlights for all switches and buttons do not work. The backlight for the cluster also does not work. The warning lights at the bottom of the cluster come on when the key is turned, but when the headlights are turned on, the interior lights (backlights) do not come on.

When you said "interior" lights I was thinking of the overhead lights which go on when you open the door. On my car the overhead lighting switch module which turns on the reading lights and selects whether the interior lights go on is super sensitive. Unless you have that slider switch in exactly the right position the interior lights will not come on when you open the door(s). But if your issue is with cluster lights, etc. then this is probably not the problem. Never mind...

Rgds,
Chris W.
'95 E300D, 444K

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Objects in closer are mirror than they appear.