(I've been poking around in the 190D's instrument cluster.)
This instrument cluster has one of the low-oil timer circuit boards on it. This board's job is to suppress the low-oil indicator lamp until the sensor reports continuously for something like 60 seconds so that sloshing in the oil pan doesn't panic the operator. Many report that these little boards stop doing their job, resulting in a lot of false low-oil indications. Nobody has been able to fix one, but not much is known about their construction. I note that it has an electrolytic capacitor on it, and these devices are known to fail with age. There also is an 8-pin DIP IC on it, in this case marked with a "v 301" legend and a date code. This is not an LM301 op-amp as the pinout doesn't match up, nor is it any related part or a LM311 comparitor as pin 4 (the negative power lead on these parts) is a no-connect on the board. The board has four pins on it that connect to the instrument cluster. I assume that these are power, ground, input, and lamp output. They are labeled KL15, KL31, GEBER, and AUSG. (15 and 31 are the standard Bosch/Mercedes legends for power and ground, and the board's circuitry bears this out. Geber is giver, or the input, and Ausgang means output.) The remaining complement of components are six resistors, and one each diode, transistor (C33725), and non-electrolytic capacitor. More as/if I find out anything. -- Jim
