Voltage Regulators, How do I test to see if it's bad? Options

[Ross]

Happy Friday Everyone,

I have found that my battery is not getting a charge from the alternator. I tightened the belt (which was loose) and that didn't help. I thought before buying a new alternator (and various other parts to go with it) that I would swap out the VR, as new ones were only around $20. Well, it turn out (of course) that I need an expensive, Bosche VR for over $200.

So now I am back to just buying the alternator, but before I do that; do you all know if there is any way to test the VR before spending the $ on the new alternator?

Thanks as always for the help!

[GregAmy]

...I would swap out the VR, as new ones were only around $20. Well, it turn out (of course) that I need an expensive, Bosche VR for over $200.

Why? Do you have something special? The ~$35 solid state Hella should work for all cars.

[Ross]

It has a whole different way of plugging in. There is a "block" on the relay pad so that only a certain style pushes into the receptacle.

[GregAmy]

It has a whole different way of plugging in. There is a "block" on the relay pad so that only a certain style pushes into the receptacle.

Then you got me (photos would help). All the relay plates on all of the cars I've seen are the same...three pins, VR pushes in from the top, held on by two screws on the side. Alternator wiring harness plugs into the plate right next to it.

Unless you have a /6? I have no idea how those are built, or if they differ.

You can actually test to see if it's the relay plate by removing the VR, removing the alt wiring harness, and plugging it straight into the VR. You must use a multi-meter to check for voltage because the "gen" light will stay on (the light is wired internally to the plate).

And if you need an alt harness, they're available new from 914Rubber.

[Ansbacher]

When my VR went bad, the casing would get extra hot to the touch.

Ansbacher

[GeorgeRud]

The connectors are the same for both the -4 and the -6. The solid state regulators work well, but the old ones can be tested and actually adjusted. You’ll need to find an old school electrical rebuilder that has the equipment, and none of the local auto parts stores will have a clue what you’re talking about. There have even been some internet sites that discuss the adjustment procedures for Bosch voltage regulators.

[GeorgeRud]

Check this site:

http://bmwmotorcycletech.info/boschmechreg.htm

[GregAmy]

Attached is what the /4 relay boards look like. VR plugs into upper right of photo, harness plugs into similar triangle plug below that.

[GregAmy]

Bottom side. And all that melted/cracked potting material is why I really prefer to remote-mount the VR, so that the amperage is not going through the relay plate. All it takes is a single (low-amp) jumper wire from the VR harness to one of the pins on the relay plate to make the dash light work correctly.

[Ross]

Thanks everyone, this is great information. I will use this as I am going to take a look again tonight.

[914Sixer]

Send me your shipping information and I will send you a brand new old school Bosch to test with. If you want I can throw in a restored relay board. Let me know.

[Drums66]

...I would swap out the VR, as new ones were only around $20. Well, it turn out (of course) that I need an expensive, Bosche VR for over $200.

Why? Do you have something special? The ~$35 solid state Hella should work for all cars.

......Borg/Warner, is another solid state brand that works fine!(if you can find it) (IMG:style_emoticons/default/idea.gif) (IMG:style_emoticons/default/bye1.gif)

[GregAmy]

Link to a thread last year where I re-mounted the VR and changed to better power fuses.

http://www.914world.com/bbs2/index.php?sho...=292455&hl=

BTW, I'm using a sold-state Hella VR now, and that top fuse is not needed.

Note the location of the heater relay "just in case" you lose the fuel pump or power relay.

Further, if you do not have a rear window defogger then that top relay is not used and becomes a handy place to store a known-good spare "just in case."

[Dave_Darling]

I believe you can jumper from the D+ to the DF terminals where the VR would plug in. That would force the alternator to go full +, and give you something on the order of 16V at the battery. Obviously you don't want to do that for long, unless you like batteries that boil over and/or explode. (Mmmm, sulfuric acid!! A face-full of that will wake you up in the morning--briefly.)

That will not specifically test out the VR, but if the alt does go full-charge, that would rule out much of the rest of the charging system.

--DD