Curse you idiot-light..
 

73 280


What looks to be the usual voltage regulator failure mode on the ole bosch alternator about nipped me this morning. I noticed on my 20 mile ride to work the wipers were getting slow but didn't think too much of it. Went to lunch, or tried to, and no go, dead battery. Jump box to running and no charge. Let me tell you, in the rain, in a hurry, it is NO fun to change the voltage regulator with the alternator in place on a 280. I've found myself again asking what in hell they were thinking putting this motor in that car, but anyway. No idiot light! It comes on with the key, but I got no warning.
I'm also not in love with my charging readings, I revived the battery with the shop charger and am showing 12.8 at idle with lights and wipers on, low 13's above idle, about 13 flat or real high 12's with no load at idle. I know the thing's 40 years old but that is kinda thin sounding to me.

On a related note, I grabbed a new voltage regulator/brush holder off the shelf at work. I have swapped these at will for years and never had a problem despite Bosch having many different numbers for them. Anyone know what the difference is between them?

Gauges. I need more gauges.

"Gauges?" "We don' need no STINKING gauges!"
-Real Life Engineers in Stuttgart.

Bosch regulators run low
 

My experience with a number of different bosch units is that they rarely go above 13.1-13.3.Sounds like yours is towards the low end of normal.How are belts looking? I had trouble with a VW alternator several years back that was the result of a poorly tensioned drive belt.Circuit integrity is important as well.Cables and connections with high resistance will lower measured voltages quite a bit too.

Well between the torrential downpours, I got to check it a bit closer. 13.5 idle no load, I can drag it down to 12.5 with the lights, wipers, heater blower and rear defroster at idle, but it would come back up to 13.3 or so with some RPM. When the belt caught anyway. So out to the shop to adjust the belt. I remember why I never snugged it up before, I ended up pulling the damn ac comp (that has a big hole in it) to get access. What a pain. But it's charging alright now I think.