If my lower harness is bad what symtoms will I have?

I believe the lower harness contains only 6 leads: a thick cable for the alternator and one for the starter; a thin wire for the alternator and one for the starter; an oil pressure sensor wire and an oil quantity wire. Maybe this will help you troubleshoot.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles

Is this the same for a '94 E320? I'm having strange electrical problems with the battery randomly draining dead in short periods of time; the low oil light's been on for a while and the oil pressure gauge has been pegged at max as well.

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Robert Fini

'12 ML350 BlueTec, 87k
'06 E320CDI, 270k
'05 T1N Sprinter 2500/Pleasure-Way Plateau TS, 69k
'97 C36AMG, 313k (son's)
'94 E320T, 249k
'93 190E Sportline LE, 168k (daughter's)
'84 190E-2.3/5spd (Stage Rally Racer)
'66 230 W110 Sedan (Barn Find, Vintage Racer build in progress)

I'm not at all familiar with the E320, but if you are having problems with both your oil pressure and quantity gauges and a random draw on the battery, I would definitely look into the condition of the lower harness. You could probably pull up a picture of both harnesses (E320 vs. E420) and compare them.

On the E420, the big wires leading to the alternator and starter are really heady duty and it's hard to imagine that they would deteriorate substantially. But the smaller wires for the oil pressure and quantity gauges as well as those going to the starter and alternator were definitely shot on mine and the car wasn't even driven in a winter climate. It is not hard to get under the car and check these wires.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles