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'82 300D
4 Posts
Discussion Starter #1
Hello all,

I would like to start off by saying that I have been watching this forum for the past month, and it has really been a deciding factor on my purchase.

I have recently purchased a '82 300D Turbo Diesel from a guy in Salem Oregon. I feel that I got the car for a great price, and I am feeling great about my decision to buy a MB.

Although I am new to the MB world, I have been an exclusive German car owner since I started driving (one BMW, and many VW's). I am pleased with the build quality of this car, even after 20+ years the doors shut the same as the showroom cars!! I purchased the car for $1800, with a spare car minus the body (motor, electrical, accessory motors, etc). The car has 300,000 miles, and a new engine as of 60,000 miles ago. The body is as straight as can be for 20+ years ( a few door dings, no scratches though), and the drivers seat shows the 300,000 miles.

The car came with a few problems that I need to address:

First is the tach, it's not working at all. I don't know if there is a problem with the gague cluster, or something under the hood. Do these cars have a crank sensor, or something along those lines? This is my first diesel that has a tach, so this part is all new to me. I'm assuming that when the engine was rebuilt, somebody forgot to connect the wires...

Second, The oil pressure gague is pegged at 3 bar, unless it's at idle, then it's right around 1.5 or so. Could this be a bad sending unit, or sensor, or is the gague the culprit? I have a spare gague assembly that I think I will switch out. The current one has a couple burnt our bulbs in it.

Third, I am flaborgasted with the fan controls (the buttons with the fan blades on them to the right of the HVAC controls). What and how do they work? I think my resistor is burnt out cause the fan only works on high. I noticed that the resistor is over $300!!! Is there a cheaper solution?

Fourth, is there a book that would be a worth while investment? For the VW's and Bimmers I always purchased a Bently manual (or for the rabbits, How to keep your Rabbit running, hehe)

So far those are the major issues going on right now.

I appreciated any feedback that people can give me to keep this car alive (other than the standard maintance issues).

I will take some pictures this weekend after I do a full detail job on her :)

Thanks in advance,

2008 PT, 1998 neon--1965 VW 1200
2,533 Posts
oil pressure is normal, mine does the same thing. you want it to be 1-1.5 bars(someone else chime in if im wrong) when the car is idling in gear and you want it to go all the way up to 45psi when it is in neutral/park or you are pushing the accelerator pedal.

the tachometer i dont have, but i hear you can stuff a cigarette butt into the sender(black, on the inside drivers fender) to re-seat the pins. seems like after years and years of diesel vibrating them, they either come loose or just dont fit correctly anymore.

doesnt seem like issues much to me! but make SURE you clean the tank screen!! and all the fuel filters. ASAP itll save you headaches and possibly dents[:)]

Premium Member
W-1-2-3 Go!
16,161 Posts
Hello and welcome! Congrats on your new ride. [:p]

Tach not working--some have said to put a cigarette butt on the tach sender, a cylindrical device on the driverside fender under the hood. It's the size of a D-battery or a 35mm film canister for 1982 models. There's a plastic tab that you can unscrew to pop it open. I don't want to ruin it for you by telling you too much as I haven't done this myself, but perhaps a search for "cigarette butt" and "tach" could help. Usually that's the common problem with high-mileage cars. I would check that the line going from that tach sender unit (grey) should lead to the engine and has no cuts or anything (to be on the safe side).

Oil pressure gauge--normal. It should idle at around 1.5 but not lower than 0.3 (somebody correct me on this).

Fan controls--left to right:


Temp wheel on left indicates what temp you want the interior to be. Buttons to right indicates what speed you want the blower to run. Upper is max at 6. Lower is minimum at 1. Middle is automatic. You let the car set it by itself according to ambient temperatures. On the dashboard is a small grille between the center vents, just above it, below the rearview mirror. That grille has a sensor within that senses cabin temperatures and tells the ACC to adjust the temperature accordingly (let it blow more air or not, etc).

You mention it only works on high. It's definitely your foam hose under the dashboard that's rotted out and needs replacing. That temperature sensor in the cabin uses that hose to give info to the blower to act accordingly. If the hose is gone, the blower will automatically blow at maximum speeds since it's not receiving any feedback. I posted a thread about disabling the center vent flaps, in there you could also read about replacing the hose. Search for "Center vents now working!" If nothing comes up try "center vents" and browse until you see the title "Center vents now working!".

Get a Haynes manual. Lots of info there as well as details like what stuff to use, how to open this, or that, etc... Also, the Online Tech Help thread pinned on this forum will lead you to dozens of sites related to the car, mostly DIY (do it yourself) stuff you can easily do if you're handy with tools. The owner's manual should also help plenty.

I'm pretty sure after a few hundred miles you'll have a sense of the car and how to drive it around. It takes a while to get used to especially if you're not a dieseler. Goodluck! Congrats! Enjoy!

By the way, just keep reading previous posts. Feel free to ask anything. I'm sure it's been covered before and others can dive in to reply. I'm sure you'll find good stuff there that you could have thought about but couldn't remember to write about (information overload [:D])

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