defalt

Hi,
I have pulled out and cleaned (no water) all the gauges on my 300GD.
The battery it has is good, already worked in the G, and charged to 13.8 V.
I have put everything back in place, according to photos I took. Two wires are not attached, a blue with red stripe and insulation on connector, and a ground wire. They are attached together (not connected) with a bit of tape.
When I try to start:
Put the key in lot;
Turn the key to position before starting; big noise, tachometer goes to 4000rpm on its own;
Turn the key to start; noise stops, tachometer stops. Clicks one time, won't start.
Any help will be MUCH appreciated. Electrical problems are the ones that I hate the most...

streborx

Elaborate on the wires taped together. This doesn't sound like the way it left the factory.

defalt

They are the same kind of wires that go to the instruments. They are taped to stay alongside each other, but not connected to each other nor to anything. The big noise is coming from the glow plug relay. This morning I tried one more time to start it, noise seemed gone and glow plug light was on but battery went too weak again. The problem may have solved itself, but I still need to check.

streborx

Wiring harnesses are usually standard, so it's common to find block style connectors for unequipped options dangling and going nowhere. Two wires as you describe sound as if they should terminate somewhere. If you have a voltmeter, is there 12 volts measurable between the two wires? If the blue/red stripe wire is 2-3 mm diameter, it's likely a power wire that's supposed to connect somewhere (signal carrying wires are usually much smaller). Absent a wiring diagram, you could try ringing its continuity to the fuse block(s) and perhaps tell from the fuse function what it's supposed to be connected to. You'll need to pop out each fuse one at a time, however, and check the wire's continuity to the "non-hot" side of the fuse (the side not connected to battery). Otherwise (assuming it is a power wire), continuity will ring through all the fuses because all eventually connect to the battery, and be misleading. If the battery went flat overnight by itself, it either has a dead cell or there's something always on that's sucking current. You can use the voltmeter's ammeter function to determine how much idle current if being drawn when the ignition is completely off -- it should be no greater than a 100 milliamperes or so. Next to an OBDII scan tool, a voltmeter is the most useful instrument you can own. Even inexpensive ones sold at box stores will do the job.

defalt

Battery tested good. My mechanic friend thought what if we changed it anyways, and problem solved. These things are weird. Battery put out good voltage, good amps and all.

streborx

Really strange battery behavior and odd the tester didn't identify it, but great to know the solution was simple. I've never owned a "d" - maybe the engine pre-heating cycle causes a different battery aging effect where volts and amps can measure OK, but its energy capacity deteriorates to where there's just not enough juice to get the job done.