Unknown Bosch component: voltage regulator? dual battery relay?

[furgo]

I've been trying to figure out what the Bosch component next to the double relay and series resistors is.

I have two batteries, so I'm thinking it might actually be the part that switches them, but I can neither quite understand the wiring nor can I identify the component itself. Here's what it looks like:

It does sport a very helpful sticker with a diagram, which also contains the part number. Unfortunately, the initial bit of the number has been erased through the years. I can only read ... 980 000 (2/81)

Label slightly edited for better readability

In terms of connections, it has 4 terminals (see pics below):
• Top right (blue) goes to the alternator connector's D+ pin
• Top left (red) goes somewhere (*) outside the engine compartment, along with the (separate) bottom right cable
• Bottom left (red), see above
• Bottom right (red) goes to the left battery's positive terminal

(*) Unfortunately I ran out of garage time and I didn't have the chance to see where the cables were actually going today

This is a '79 2.0l FI Federal Westy.

Any ideas?

[aeromech]

That sure looks like a generator voltage regulator to me but I can't understand why it's in your bus. The normal location for the correct type is in the forward r/h side of your engine bay.
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[furgo]

Thanks for the reply. I actually considered that for a sec too, but what confused me was:

1. If that's the voltage regulator, what's the black box on the right hand side the voltage regulator connector plugs into? Strangely enough, searching for voltage regulator pictures on buses, none of them look like that plastic black box. They seem to be bulkier and with a metal case. I'm thinking I might have to take that box apart tomorrow:

2. The (I believe) older mechanical voltage regulators do look the same wrt the case, but seem to have a different label and entirely different circuitry. I just found this one on the gallery, for instance:

VR from someone else's bus

[aeromech]

Telford Dorr would be the person to ask. My only guess is that the original VR crapped out and someone slaved in this one.
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Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
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[busdaddy]

That sticker is interesting, it does seem to depict 2 batteries, need someone with German skills to translate.
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[furgo]

[sodbuster]

I'd say someone was trying out an old generator type voltage regulator to fix their charging problem, is exactly what is going on here.
The original voltage regulator for your bus did come encased in a metal body. But Bosch replacements did also come with a plastic body. So I'd say it is a good chance the (stock for your bus) voltage regulator you have that was bypassed is most likely correct just bad operationally.

My vote is to find the correct regulator and restore the wiring harness back to what it was.

[furgo]

I do believe it was as you and aeromech are suggesting.

And to replace it with the original was my initial idea, after having fixed the cables wrapped in electrician's tape first!

But given the fact that I've got a dual battery setup and I still don't know exactly why that particular voltage regulator relates to that makes me unsure –I'm still trying to find out how the PO wired the two batteries too.

In any case, doing some quick research on microfiches for late bays, it seems getting the original component boils down to:

VW 113 903 803 C, 113 903 803 D or 113 903 803 E. Only the last one seems still available
http://www.volkswagen-classic-parts.de/en/spannungsregler-b30ee7.html

VW 211 903 803 E
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1332359

However, another puzzling bit is that none of those match my wiring harness. That is, they've got single terminal or spade connectors, whereas I've got the 3-wire black connector coming from the harness.

It seems that in that case (I guess later buses) there was no VW part listed? All I could find was directly from the original manufacturers:

Bosch 0 190 601 006
https://www.thesamba.com/vw/forum/album_page.php?pic_id=1172263
https://www.thesamba.com/vw/forum/album_page.php?pic_id=1172264

Motorola 043 903 803
https://www.thesamba.com/vw/forum/album_page.php?pic_id=1166807

And perhaps HELLA 5DR 004 243-111?

Anyone around with a bus with the black voltage regulator connector around to share which part number they've got for the regulator itself?

Thanks!

[busdaddy]

[TomWesty]

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[furgo]

[telford dorr]

My best guess it that it's a dual battery relay, built using a generator voltage regulator case. It's probably a voltage regulator without the regulator relay installed, just the cutout relay. As this relay is rated for the service, it makes sense. The label shows it connecting two batteries together, so that kinda confirms it.

Note the second coil from B+ to 86: it's slash symbol is opposite of the main coil (61 to 31). To me, this implies that it is a bucking coil which opposes the main coil. This means that if the main battery is pulling a lot of current on startup, this current would oppose the main coil and keep the second battery from being connected. Once the main battery charges up, the current falls off, and the main coil pulls in, connecting up the second battery. (Once the relay pulls in, the second coil probably has little effect, [it takes much more magnetic field strength to pull in a relay than it does to keep it in] thus the 'house' battery can pull lots of current without the relay dropping out.) Thus, the main battery has priority over the 'house' battery. Clever Germans...

Note to self: if hard up for a dual battery relay, and nothing else is available, use an old defective generator voltage regulator and hack off the vr relay...

Nice enhancement on the label. by the way. Much easier to read!
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[furgo]

Awesome, thanks so much everyone!

I'll try to confirm tomorrow, but it seems the mystery is solved

[furgo]

So mystery solved:

1. That black box on the right hand side is a solid state regulator (HC-CARGO 130675 https://www.hc-cargo.com/default.aspx?id=7&productid=130675). I've not tested it, but I assume it's working.

2. The mystery component is indeed a 12V 40A dual battery relay. I could find the part number at the bottom side of the case: 0 333 304 001, and there is a datasheet available on the Bosch site (which does not add to much info, tbh).

I've not found it in many places on the net, but here are a couple of pictures from such a part from external sites:

http://www.oldtimercentrale.be/autopart.cfm?icat=301&i=3591
http://www.ebay.de/itm/BOSCH-Batterie-Trennrelais-...1757811523

In terms of the pinout:

• Top right is 86
• Top left is 61
• Behind top left, not too visible is 31 (chassis ground)
• Bottom left is B+
• Bottom right is 87

One thing I noticed is that whoever mounted it did not connect terminal 31, I guess thinking that the case to firewall connection would be a good enough ground return path. Not so sure about that given that the firewall is painted and current probably flows through the mounting screws, but it seems to work.

Notice the screw on terminal 31 behind terminal 61 (blue cable)

So as far as I understand it, the whole dual battery + alternator + voltage regulator setup in my bus looks like this:

Also from the Bosch datasheet I downloaded from www.bosch-classic.com (I don't think I'm allowed to redistribute it), the internal schematic looks slightly different with regards to the coils' illustration:

I don't quite grasp how the dual battery switching is supposed to work, and in particular two things:
• Why is there an internal winding between terminals 61 (indicator light) and 31 (chassis ground) instead of a straight connection? Does it have any effect on the switch?
• Is the internal switch that closes terminal 87 N.O. as depicted on the part's sticker and in my hand-drawn diagram, or is it supposed to be N.C.?

Comments appreciated. Thanks!

Update: I just noticed Telford Dorr added some additional info to his post from yesterday (thanks!), so the first question is probably answered, although it's still taking me some time to digest the info and actually understand how the circuit works. The reason I'm trying to delve into it is also because I'd like to find out why the alternator light always remains on for quite a few minutes after the bus has started and it's on the road.

[busdaddy]

Both of those diagrams you've drawn make sense, some terminal numbers are swapped in each.
On the Bosch data sheet one 86 would be B+, it passes current all the time to 51 (starting battery), that creates a normal battery connection like you'd find with no relay installed. When the alternator starts charging the blue wire powers 61 and creates a magnetic field in the coil grounding through 31. Current passing from 86 to 51 also adds to that field through another set of windings in that coil, the combined fields are enough to pull the contacts closed and pass current from 86 to 87 connecting the aux battery to the system.

There could be another way it works as well, the magnetic fields may oppose each other until the main battery has reached a state of charge sufficient to reduce the load on the alternator, when that happens the current from the charge lamp coil can close the contacts and proceed with charging the aux battery, either way will work but the second method would reduce the initial load on the alternator. Knowing the Germans this is more likely, a simple relay that connects both batteries whenever the charge light goes out would be much more simple, but impart a greater load on the alternator if the aux battery was severly discharged.

The contacts should remain open when not in use, that allows the aux battery to be run down dead without discharging the starting battery.
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