TheSamba.com :: View topic

Sat Mar 20, 2010 10:31 pm

My Safare' is having an over charging issue. It has been going on for a while now and I can't seem to be able to figure it out.

Basically the alternator just keeps on charging full bore no matter what. I have tried 3 different regulators now and still nothing. The only thing I can think of is maybe something messed up in the wiring where the wires from the alternator, regulator, and to the dash are messed up somehow. Maybe even something in the dash for the idiot light.

Could someone shed some light on this and maybe post up a wiring diagram for just the charging system?

Thanks! :)

Sat Mar 20, 2010 10:44 pm

Overcharging is sometimes misdiagnosed. People see bubbling and or gasses escaping and decide the system is overcharging. Mind you I am not saying it is not. But there are two questions that need to be answered before one decides it is over charging.

What DC voltage is present between the battery posts when this is happening?

Have you checked for the presence of AC in the system? A blown or leaky alternator diode will cause a battery to act similar to overcharging.

Sat Mar 20, 2010 10:50 pm

I've put a meter on it and seeing 15 then 16 volts, I call it overcharging. :lol:

I'm not sure how to check for alternating current in DC systems, but I'm fairly sure that if a diode went to hell, my battery would discharge. That doesn't happen.

Sat Mar 20, 2010 11:15 pm

If you're seeing 15 - 16 volts, you definitely have hyper-active alternator. Try this: reconnect your voltmeter across the battery, then disconnect the "Df" wire that goes from the regulator to the alternator. Run the engine. If you still get the high voltage across the battery, then the problem is either a short of some kind inside the alternator or in the wiring between it and the regulator (most likely between the "Df" and "D+" wires - could also be swapped). Remove the alternator and wiring and bench test (or take it to your FLAPS), and check all wiring and connections.

If the symptom goes away, then something's messed up with the regulator or the connections to it.

Tutorial: the regulator applies voltage to the Df wire, which causes the alternator to convert rotational energy to electrical energy and thus charge the battery. When the voltage exceeds a temperature variable setpoint (somewhere around +14.4 volts), the regulator turns off the voltage on the "Df" wire, causing the alternator to shut down. In normal operation, the regulator will continuously apply and remove voltage from the alternator, at high frequency, causing it to effectively maintain a fully charged battery without overcharging it. The regulator is initially activated by voltage applied to it via the charge indicator bulb in the dash (which is why the battery doesn't charge if this bulb burns out.)

P.S. you're correct on the bad diode - battery will discharge through it, generally cooking the alternator stator windings in the process.

Sun Mar 21, 2010 9:05 am

I just went through the same thing! I had installed a new (rebuilt) alternator and it continued to over charge. I changed the regulator and it still did the same thing. After taking the alternator in and out twice to have it tested, it was a BAD alternator!!

Sun Mar 21, 2010 9:18 am

best 12 bucks you can spend

http://www.amazon.com/Equus-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=pd_sim_auto_1

Sun Mar 21, 2010 9:20 am

Telford, do you have a wiring diagram for those connections? Like what colour wire goes where and does what? The wiring at those connections does look hacked by the PO, so I'm not sure where to start.

I do have a spare alternator sitting here, so if it comes to that, I can swap it out.

Sun Mar 21, 2010 10:00 am

Quote: do you have a wiring diagram for those connections? Like what colour wire goes where and does what? The wiring at those connections does look hacked by the PO, so I'm not sure where to start.
Look in the "technical/wiring/1973-74" pull-down on this site. You're interested in drawing columns 1 through 3 on the left page.

In summary, there should be three wires going between the alternator and the regulator: a brown ground wire between the "D-" terminals; a green drive wire between the "Df" terminals, and a red voltage sense wire between the "D+" terminals. The red wire also supplies power for driving the alternator rotor. Finally, there is a blue wire going from the regulator "D+" terminal into the harness. This is the wire that goes to the indicator light on the dash. [The other side of the light is fed +12 volts from the keyswitch.]

Drive to the alternator rotor is supplied to the regulator, initially via the blue wire, but operationally via the red wire; leaves the regulator on the green wire, and returns on the brown wire; finally returning to ground via the mounting between the regulator and the bus body. The red wire also senses alternator voltage and the regulator uses it to control the alternator output. The regulator needs to be well grounded to the bus body. The engine also needs to be well grounded to the bus body (via a wide ground strap from the front of the transmission to the frame.) Check these grounds carefully, removing and reinstalling to freshen up the connection.

Sun Mar 21, 2010 10:01 am

alteranator is C, Regulator is C1, K2 is charging light, Wire colors are what the factory used. Alternator circuit is to the left on the first page below.

http://www.thesamba.com/vw/archives/info/wiring/baybus_7374a.jpg

http://www.thesamba.com/vw/archives/info/wiring/baybus_7374b.jpg

http://www.thesamba.com/vw/archives/info/wiring/baybus_7374_key.jpg

http://www.thesamba.com/vw/archives/info/wiring/baybus_symbols.jpg

Sun Mar 21, 2010 10:28 am

Alright. Just went out and looked. I got a brown, green, and red wire from the alternator connecting to the regulator. The blue wire heads for the dash as it should. Then I also got a black wire going from the alternator that goes along side the blue wire and heads for the dash too. (at least I think it goes to the dash)

I'll try to snap a pic.

Sun Mar 21, 2010 10:38 am

if the black wire comes off the same terminal as the red one, it is the test network wire shown in the schematic.

Here is a cutaway of the alternator and VR section of the schematic

Sun Mar 21, 2010 11:12 am

Ok, here's a few pics. Pardon the dirt, I live down gravel roads, so I pick up a lot of dust. But I assure you there is no rust under there. 8) Been meaning to clean it out. I also had electrical tape covering the connections so there was no shorts, just took it off for the pics.

Tue Mar 23, 2010 10:06 pm

So does anyone have any more insight?

One more thing that might be worth mentioning is that if I start the engine with the plug connected to the voltage regulator, it will start charging as expected, but if I unplug it while it is running, it still charges. Starting while unplugged gives no charging.

Wed Mar 24, 2010 9:38 am

You need power on D+ to initiate charging. Once charging is initiated the power can be removed and it will still charge.

As a guess I would say you have a problem in the harness. You need to check for continuity between various wires and between the wires and ground.

Wed Mar 24, 2010 6:26 pm

Alright. I'll start checking stuff out.

Wed Mar 24, 2010 9:58 pm

Quote: So does anyone have any more insight?

One more thing that might be worth mentioning is that if I start the engine with the plug connected to the voltage regulator, it will start charging as expected, but if I unplug it while it is running, it still charges. Starting while unplugged gives no charging.
You just found your problem.
Now pull the alternator and the wiring harness attached to it. Detach the harness from the alternator and check for a short between the red and green wires. Flex it while testing. Shorted? Repair or replace the harness. No short? Replace the alternator.
The alternator can't put out any power with the regulator disconnected.

Thu Mar 25, 2010 2:04 pm

Good to hear. I'll check it out soon. It decided to get cold, snowy and windy here over the past few days, but supposed to be warm this weekend.