I recently acquired a 1995 300SD Turbo as a secondary vehicle for long road trips - I was looking for something a bit more appropriate for business trips than my well-worn 1995 Ford Ranger. I wanted something presentable, comfortable, and economical, so I think I got what I'm looking for. However, I recognize already that I have some maintenance work to do before the vehicle is reliable enough to be driven 400-500 miles away from home. There are some suspension issues I need to take care of, but my main concerns have to do with the electrical system, primarily gradual discharges that keep the car from starting. I'm trying not to be a complete clueless newbie, so I have done some research and learned about the blown fuses, blower fan problems, weak alternators, and trunk lights that stay on when the lid is closed. I'm also carrying around a multimeter and taking notes when I encounter problems.
Here's what I have noticed so far:
(1) I am noticing gradual discharge when I operate the vehicle at night - not so much of a problem during the day. The combination of headlights and heater blower seem to cause the most trouble (fuse #16 blows from time to time, which I believe is the heater fan). The battery light comes on ever so dimly at idle as well. I did a static test running the car in idle with a fully charged battery (12.3 V) and noticed that the heater was responsible for an 0.3V drop and the headlights for an 0.5V drop - how significant this is I am not sure.
(2) I get intermittent "clicking" sounds from inside the dash (sometimes near the steering column, sometimes near the heater console) when the system starts slowly discharging.
(3) The battery never really dies, or even comes close to it - the clock keeps running, and even the headlights will come on moderately bright (I do lose the radio presets, however). I have checked the battery voltage, and found that it the starter turns slowly below about 11.5 volts, and simply clicks once and does nothing below about 10 volts.
(4) My (diesel) fuel gauge seems to migrate quite a bit, even when accounting for changes in level between going uphill and downhill. However, when I get down to "bingo fuel" (less than a gallon), the fuel low light will extinguish and the fuel gauge will go back UP to about 3/4 of a tank.
(5) My glow plug lights no longer come on. I haven't established whether the glow plugs are indeed bad or whether I just have a burned-out light, but the vehicle still starts in the morning (temperature usually 8-12 C, not too cold).
(6) Issues attributable to other problems, such as vacuum leaks (engine slow to shut down, acceleration even more gutless than expected) have been pretty much resolved.
Any suggestions from experienced individuals in this area would be greatly appreciated. Thanks in advance.
Stan de SD
1985 Mercedes 300SD (293K)