W110 W111 W112 Sedan, BENZ AID - COMMON QUESTIONS AND ANSWERS

1979 300TD No Heat!

My heat has stopped working just in time for the cold weather! The temperature control unit works fine except for the complete lack of heat (the buttons all seem to do what they're supposed to). The heat gauge on the dash shows that the engine is getting hot, but none of the temp. control settings (defrost, bi-level, etc.) make hot air blow. The air coming out of the system is the outside temp.-frigid! I recently rebuilt the vacuum pump after the diaphram tore and a little oil got in the lines. But this sounds like an electrical problem, no?

I recently got the Mercedes factory HVAC manual, but I don't know where to start with this problem. I have the vacuum and wiring diagrams and now have a rough idea of how the system works (it's complicated!).

Chassis Model Number

W123

Forums

Body and Interior Specific Aid

1981 240D Idling rougher after valve adjustment

Before valve adjustment, car idled fine. Immediately after valve adjustment car idled fine. Probably after 1,000 miles of driving, car idles rough at a stop in drive or in reverse but idles fine in park. Another change is that it has gotten cold. This was a florida car and not used to the cold. I did install a block heater from you which helped with cold starts.Turning the idle adjustment knob on the dash to the left increases RPM and helps idling.

1.How do I adjust the idle so it will run right again without having to adjust the idle knob on the dash?
2. Is it ok to drive the car with the idle adjustment knob turned to the left a little bit?

Chassis Model Number

W123

Forums

Diesel Engine Specific Aid

82 300D: Starter slow/nonexistant, replacement needed?

I have an '82 300D. When I try to start it, especially when it's cold, the starter works very slowly and feels like it is about to die. Seems like a dead or dying battery, but tested it and it's fine.

However when I hit the gas pedal when cranking, it does catch and start. This problem is especially harsh when the car is cold.

Do I need to replace the starter? Is there something else I'm missing? This car is my daily driver and I use it to cart my kids around and get to work, so I'm afraid to be stranded.

Thank you!

Chassis Model Number

W123

Forums

Diesel Engine Specific Aid

1975 240 D Electrical Power For Radio

I do not have any power to the electrical supply to the radio. Just bought the replacement fuse set from Kent and have cleaned all terminals and replaced every fuse. On the fuse box lid there is not an indicated fuse for the radio. So,,maybe I am not looking in the right place. Where is the fuse for the radio supply?

Thanks,
Tom Smith

Chassis Model Number

W115

Forums

Diesel Engine Specific Aid

1984 300D Injectors Replaced, still rough

I just purchased some rebuilt injectors (the Monarchs on this site) and replaced them over the weekend. I did a valve adjustment while i was at it. Put everything back together and she started up after some cranking, but it didn't fix the very rough running of the engine. I'm happy to have the new injectors in there as I was due for them, but now I have to run down the problem. Think it could be the injector pump? Seems like a cylinder may not be getting fuel, or perhaps very little fuel. How can I check to see if the injector pump is working properly (or any other ideas)?

Chassis Model Number

W123

Forums

Diesel Engine Specific Aid

81 240D new voltage regulator squealing

Since my 240D's alternator clearly wasn't charging anymore, I figured I first better replace the voltage regulator. The old regulator was clearly shot, and I got the new one in. Now the alternator is charging fine, but it is also making an intermittent loud squealing noise - especially when accelerating. Any chance this noise will go away or diminish as the new brushes "break in", or is it time for a new alternator?

Chassis Model Number

W123

Forums

Diesel Engine Specific Aid

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