Don't shoot the OVPR!

[G3maw]

Had recent poor cold starting problems and instantly started to suspect that oft-cited villain the over votage protection relay, next to the ECU behind the battery on my '89 190E. Checking the 10 amp fuse on the top of the relay ( OK ) and the output from pin 87 ( 12 volts, so also OK ) deepened the mystery. I was all set to pull the Air slide valve ( cold start valve ) when the two watt bulb in my head came on and I decided to check the battery voltage ( 12.4 volts - not bad but not brilliant ). With the engine running at 1500 rpm the voltage WAS THE SAME. There had been no indication of this state of affairs from the alternator warning light, which had stayed off throughout all this. But the alternator was, indeed, the culprit. Seems that the voltage regulator also adds to the confusion in this situation. A problem shared........