TheSamba.com :: View topic

Thu Feb 16, 2017 1:05 pm

I have a 1977 based type 4 engine in my square back. A couple of days ago, the alternator quit charging, and the idiot light does not come on with the key. Also, the alternator has an external regulator. I have the bus Bentley coming in the mail, but until it gets here, does anyone have any pointers that I can use to begin my trouble shooting?

Thu Feb 16, 2017 1:14 pm

Ground the blue wire from the regulator to the front, if the light doesn't come on with the key on the problem is a bad bulb or the wiring in the dash.

Thu Feb 16, 2017 1:24 pm

Multi69s wrote: I have a 1977 based type 4 engine in my square back. A couple of days ago, the alternator quit charging, and the idiot light does not come on with the key. Also, the alternator has an external regulator. I have the bus Bentley coming in the mail, but until it gets here, does anyone have any pointers that I can use to begin my trouble shooting?

Idiot light needs to work for alternator to charge.

If idiot light burns out, alternator no chargey.

So do what busdaddy said and replace bulb if it's burned out.

Thu Feb 16, 2017 2:15 pm

sjbartnik wrote: Multi69s wrote: I have a 1977 based type 4 engine in my square back. A couple of days ago, the alternator quit charging, and the idiot light does not come on with the key. Also, the alternator has an external regulator. I have the bus Bentley coming in the mail, but until it gets here, does anyone have any pointers that I can use to begin my trouble shooting?

Idiot light needs to work for alternator to charge.

If idiot light burns out, alternator no chargey.

So do what busdaddy said and replace bulb if it's burned out.

This must have changed from 1970 then. My bus just got its generator light working (previously not even wired) and ive driven a few hundred miles without it.

Thu Feb 16, 2017 2:31 pm

Spike0180 wrote:
This must have changed from 1970 then. My bus just got its generator light working (previously not even wired) and ive driven a few hundred miles without it.

Ah grasshopper, but generators are not alternators! :D

Thu Feb 16, 2017 5:22 pm

You can drive a long time on battery only. But as far as the gen/alt light all is same.

Thu Feb 16, 2017 6:30 pm

Ok,

Grounded blue wire, light came on. Is there a thread somewhere where someone went through a test procedure?

Thu Feb 16, 2017 6:51 pm

Have a look through these: http://www.thesamba.com/vw/forum/search.php?search..._chars=200

I always start with a good close look at the connectors and wires, it's not uncommon for a wire to break inside the insulation yet still look fine outside, sometimes they also push back out of the plug when connecting. After the visual use an OHM meter to confirm each wire is doing it's thing, even while pulling and wiggling the plug at each end.

Fri Feb 17, 2017 5:29 pm

sjbartnik wrote: Spike0180 wrote:
This must have changed from 1970 then. My bus just got its generator light working (previously not even wired) and ive driven a few hundred miles without it.

Ah grasshopper, but generators are not alternators! :D

Check his signature: 1700 T4 in a '70 body. So it would be a gen light with an alternator. :P

Robbie

Fri Feb 17, 2017 8:46 pm

It's kind of ironic, but there doesn't seem to be a good procedure anywhere for trouble shooting the regulator / Alternator. I've searched here, and my bus Bentley came in. The Bentley goes in depth on a generator, but it seems like the alternator was an after thought. I remembered that I had a Clymer 411/412 book. It does a great job on showing how to disassemble and test individual parts on the alternator, but nothing on determining whether the problem is the reg or alt in the first place. I refuse to spend $$$ chasing a problem. I am looking for any kind of procedure that will tell me which part of the charging system is causing the problem.

Fri Feb 17, 2017 9:19 pm

Sadly there's not many tests you can do on a regulator without a full bench simulator, some old school electric shops may still have such a rig gathering dust back in the corner. There are tests for the alternator so you can rule it out and blame something else, aside from the wiring and the regulator there's not much else to blame once that's done.

Fri Feb 17, 2017 11:41 pm

Check the slipring brushes as well. Test by measuring resistance between DF wire from alternator and earth.

Sat Feb 18, 2017 9:22 am

You can quick-check the alternator for functionality with a quick rewire using some jumper wires. This is NOT a definitive test of the alternator, but will tell you if the regulator is the cause of the problem. Basically, we're going to remove the regulator from the circuit and run the alternator "wide open", varying the alternator output by varying engine speed. If your battery is good, this is safe for a short period of time. Note: I generally don't recommend doing this if you have FI, as FI can't take a joke.

Here's the stock alternator wiring:

What we're going to do is unplug the regulator and, using some jumper wires with blade terminals on their ends, connect the regulator wires as follows:

- D- wire to ground
- Df wire to D+

This will apply maximum rotor current to the alternator.

Connect a good voltmeter across the battery and start the engine. Watch the voltmeter carefully. Increase engine speed slowly. The battery voltage should increase. DO NOT allow it to rise to more than 14.4 volts, or 2500 rev/min max. If you can get the 14.4 volts, then the regulator is probably toast.

Note: for this test to work, the dash idiot light must illuminate when you first turn on the key, as it supplies the initial alternator activation current.

---

If you have access to a variable voltage power supply (or a "stupid' battery charger and a Variac), the regulator may be easily checked. Here's the test setup:

As you increase the power supply voltage, the test light will illuminate. As the voltage gets past somewhere around 13.8 to 14.4 volts, the light will suddenly go out. Decreasing the voltage will cause it to suddenly come back on. If it does this, the regulator is working. Note: if the regulator is a mechanical unit, don't let it run very long at the 'test light out" point, as it doesn't like it (the resistor on the bottom of the regulator will get quite hot). Ironically, the solid state regulators don't care.

Sat Feb 18, 2017 1:15 pm

Thanks telford that's what I was looking for :D

Fri Feb 24, 2017 11:37 am

Telford,could you wire a rheostat to the pos post of the battery to use as a variable power supply?

Fri Feb 24, 2017 11:44 am

In this case, no.

- it would have to be one hell of a big rheostat. [You can do it easily with a small pot and a couple of transistors.]

- in this case, you need greater than battery voltage for the test.

Sorry. Good idea, but this time, no cigar...

Fri Feb 24, 2017 2:00 pm

telford dorr wrote: In this case, no.

- it would have to be one hell of a big rheostat. [You can do it easily with a small pot and a couple of transistors.]

- in this case, you need greater than battery voltage for the test.

Sorry. Good idea, but this time, no cigar...

You just need the ubiquitous step-up rheostat.

You can also take the extra voltage and charge your battery with it.

:shock:

Wed Mar 01, 2017 12:21 pm

telford dorr wrote: You can quick-check the alternator for functionality with a quick rewire using some jumper wires. This is NOT a definitive test of the alternator, but will tell you if the regulator is the cause of the problem. Basically, we're going to remove the regulator from the circuit and run the alternator "wide open", varying the alternator output by varying engine speed. If your battery is good, this is safe for a short period of time. Note: I generally don't recommend doing this if you have FI, as FI can't take a joke.

Here's the stock alternator wiring:

What we're going to do is unplug the regulator and, using some jumper wires with blade terminals on their ends, connect the regulator wires as follows:

- D- wire to ground
- Df wire to D+

This will apply maximum rotor current to the alternator.

Connect a good voltmeter across the battery and start the engine. Watch the voltmeter carefully. Increase engine speed slowly. The battery voltage should increase. DO NOT allow it to rise to more than 14.4 volts, or 2500 rev/min max. If you can get the 14.4 volts, then the regulator is probably toast.

Note: for this test to work, the dash idiot light must illuminate when you first turn on the key, as it supplies the initial alternator activation current.

---

If you have access to a variable voltage power supply (or a "stupid' battery charger and a Variac), the regulator may be easily checked. Here's the test setup:

As you increase the power supply voltage, the test light will illuminate. As the voltage gets past somewhere around 13.8 to 14.4 volts, the light will suddenly go out. Decreasing the voltage will cause it to suddenly come back on. If it does this, the regulator is working. Note: if the regulator is a mechanical unit, don't let it run very long at the 'test light out" point, as it doesn't like it (the resistor on the bottom of the regulator will get quite hot). Ironically, the solid state regulators don't care.

Telford, a couple of questions.

When testing the regulator you show D- going through the regulator and back to common on the power supply. Is it supposed to ground through the body of the regulator? My regulator has no continuity between D- and the shell.

As for the alternator, the only way that I can get the dash light to illuminate is when I ground the blue wire. I checked the wiring and the signal from the blue wire is going to the D+ of the alternator.

This would lead me to believe that something in the alternator is not allowing the activation current to energies the alternator. Or am I way off base?

Wed Mar 01, 2017 12:34 pm

Abscate wrote:

You just need the ubiquitous step-up rheostat.

You can also take the extra voltage and charge your battery with it.

:shock: Commonly referred to as the Transfrheostormer.

Wed Mar 01, 2017 12:36 pm

Multi69s wrote:

Telford, a couple of questions.

When testing the regulator you show D- going through the regulator and back to common on the power supply. Is it supposed to ground through the body of the regulator? My regulator has no continuity between D- and the shell.

Yes, the regulator body should be grounded. Telford mentions that in page 1 of this thread:
http://www.thesamba.com/vw/forum/viewtopic.php?t=673255