The VW Bosch Regulator is 30 Amps and not suitable over-stressing the Generator compared to the SF?s 11 Amp Bosch Regulator. Wolfgang has the proper 11 amp Regulator.
Pull the Rubber Plug out of the Brush End of the Generator and ensure the small Bolt through the Terminal you see there is not the culprit.
A big problem with the SF Regulator is Vibration; such that, you must ensure it is adequately Rubber Mounted even if you have to fabricate the mount. I rebuilt my mounts using a Spark Plug Rubber Boot.
I have no problem running an 85 Watt Halogen Head Light, 2 x's 35 Watt Fog Lamps & keeping a sYTX14-BS Battery Charged. I do a lot of Night Riding with 200 mile runs back to home base after a day of cruising.
You might find this Info useful:
11 AMP BOSCH REGULATOR Terminals
B+ - To Battery
D+/61 - To Generator D+ and Battery Warning Idiot Light
DF - To Generator DF Terminal
D- - To Generator D- (GROUND?)
Do Not forget to Ground the Regulator Base Plate to the Frame.
A Fully Charged 12 Volt Battery should have a minimum of 12.6 Volts but can be as hi as 12.85 Volts
NOTE that the Generator is specifically wired for the BOSCH Regulator and the Field Coil Terminals
within the Casing must be changed if using a Lucas & most aftermarket Regulators. Very similar
to Wiring the Brushes and Field Coils to Work in a Series rather then Parallel. Bosch Sites have
the Wiring Terminal Modification.
Check the Charging Voltage -
With the engine running at above idle speeds, the voltage across the battery terminals should rise to 14 - 14.5 volts - I've found a minimum of 13.25 Volts is OK with the 750SF - (7 - 7.2 volts for the 6-volt system). If you are getting that voltage, the battery is receiving a normal charge.
If you don't see that voltage, try pressing the brushes in (against the commutator) while the engine is running (mind out you don't touch the spinning pulley!) The upper brush is easy enough to reach, the underside one is rather more difficult. You can use your finger (14.5 volts won't electrocute you
or the back of a small screwdriver, but nothing metal please.
If the voltage shoots up to 14-14.5 volts (7-7.2 volts for the 6volt VWs) when you apply pressure, the brushes are worn to their limits and should be replaced.
Check the Maximum Voltage of the Generator -
1. Disconnect the generator from the regulator (both the DF and D+
wires).
2. Use a jumper lead to connect DF to the generator frame (grounding
the DF connection).
3. Now start the engine and test the voltage between D+ and the generator
frame.
4. The voltage should increase with rpm up to about 35 volts (20 volts
or so for the 6-volt generator).
5. If the generator passes this test, it's working okay.
DON'T run this test any more than a few seconds -- just enough to make
the test at increasing rpm, as this test will heat up the generator.
Polarize the Generator -
If the above test fails, it may be caused by the generator becoming depolarised (not enough magnetism to start the generating process).
To polarise the generator, remove the fan belt, jumper wire from DF to the generator case (grounding the DF terminal). Now connect a wire from the + terminal on the battery to D+ on the generator. The generator should now start to spin. A few seconds is enough for this test.
If the generator doesn't spin, it's faulty. It's rebuild time (or at least it needs an auto electrician to look at it).
Check the Results -
Now put the fan belt back on, leave the DF terminal grounded, and check for the high voltage from D+ to ground with the engine running at high rpm. If you don't get the high voltage (up to 35 volts for the 12-volt generator or 20 volts for the 6-volt generator), the generator is probably faulty.
If you get the full voltage, but when it's all connected back up and you don't see the normal charge voltage at the battery (14.5 volts for 12-volt generators or 7.2 volts for the 6-volt generator), the regulator is probably faulty.
Hopefully these tests will identify your problem and you can get it fixed yourself without great expense. You'll have learned more about the electrical systems in a car, and won't get stuck at a critical time with a dead battery.
