Alternator problem -- loose wire

[stratamarr]

OK so I think I may have an issue with the alternator recharging the battery. I went through the forums and may have partially solved it but I think there may be something I'm missing.

Was seeing the red indicator light turn on when at idle. Read many, many forum posts about voltage regulators and alternators. Viewed a lot of Youtube videos on alternators and a few on alternators that have external voltage regulators. Checked my battery with car off, 12.6V, battery is <1 year old. Started engine, voltage dipped but stays steady at 12.4V, alternator spinning with no visual issues. With 2000 RPM, voltage at 13.4V. Checking through the extra supplies from previous owner, found what looked like a "new" Bosch, still in the box voltage regulator. Decided I would give it a try and swapped with the old regulator. Success! no more red light at idle. But my test at battery never leaves 12.6 at idle, only when the engine is revving does it go up. I retested the negative battery to what I think is D+ at the alternator and it's also 12.6. Good, juice is flowing but I thought my battery should be at mid 14 V at idle.

Should I just bite the bullet and get a new alternator? I believe I have a 35amp one.

Also I took a picture of the alternator and there's a loose wire looking for a nut and bolt, where should that go?

Finally, let me say this site is fantastic. Such a wealth of information and personal experience on all things Pagoda. I doubt I would feel I could keep my car long term without you all.


Greg

[BobH]

Hello, this has recently been discussed and i took the battery readings of my car, have a look here

https://www.sl113.org/forums/index.php?topic=36737.0

You might also want to check the belt tension, but your readings aren't that far away from mine, perhaps if the belt slips it could explain the ignition lamp on, but it looks like you cured that

Terminal D+ should read the same as the battery voltage, so all seems to be ok

Not sure about the loose wire, keep searching and you may find something, have a look in the technical manual and the wiring diagrams.  Hopefully someone with more experience may also have some suggestions

[Cees Klumper]

The loose wire looks to be connected to a radio noise suppression condensor of some sort. Not sure whether it should connect to '+' or ground.

[BobH]

Looks like Cees is correct, have a look here, might be slightly different for your car.  The body of the unit is grounded, so the lead needs to be connected to one of the terminals, perhaps it was disconnected at some point because it failed or was no longer required

https://www.sl113.org/wiki/uploads/Electrical/Bosch_230SL_Suppression_Instructions.pdf

[rwmastel]

That's a great document, Bob!  Our wiki (tech manual) is full of interesting stuff.  I have the radio noise suppression option on my data card, so I'll be printing this and checking out my car.

[stratamarr]

Thanks all. Learn something new every day. Noise suppression -- never knew that this was even an option. I'll probably leave it off for now as it doesn't have anything to do with power output on the alternator (that I know, any armchair or actual electricians can chime in).

I did check the belt tension and I can move the blades a little with some force, but it doesn't feel exceptionally loose. I read in one of the forums that you shouldnt be able to move the blades at all. I'll go back and re-read that response.

Still I'm left with the feeling there should be some boost of voltage to the battery at idle, if you have headlights, heater and radio on and only 12.6V it strains your battery and will shorten its life.