Troubleshooting generator

[bnam]

Was working on the 71 Bus as it would not idle properly and would die when throttle was opened. The engine harness was hacked together and also rat bitten. So, I stripped it down and and rebuilt the engine harness.

The voltage regulator was a local old lucas style one and the voltage would vary from 10V to 16V when revved (measured between D+ and ground) - so it needed replacing. We had a new bosch electronic regulator so I also installed that. Also a new battery VW battery +ive harness. All wires were of correct gauge and crimped with OE style connectors.

After changing that and the spark plugs the engine fired right up and runs beautifully. But, the generator now does not charge.

Voltage measured between D+ and ground is now only 0.5-1.5V when revved. I also tested the no load voltage as described in Bentley -- disconnect wire from battery at the VR, connect negative of the multimeter to VR ground, and +ive to B+. Per Bentley it should read about 13.5V -14.5 at 2000rpm. I got nothing.

I'm a bit stumped now - dynamo was working before we changed the wiring. The new wiring is correct -- have triple checked it. And it's pretty simple.

While removing the leads from D and DF, the studs did turn around. Could it have broken inside? Should I check for continuity from D+ to D- (it just struck me as I was typing)?

Any other suggestions?

Thanks
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[VWLover77]

I've had some generator issues myself recently....

Your output test confused me. The one I ran was:

1. Disconnect both wires at the generator and make sure they are well protected so they don't short out on anything.
2. Attach a wire from the DF terminal on the generator to ground.
3. Start the engine and measure the voltage at D+. As you rev the engine, it should increase quite a lot. Mine went to almost 50V.

Do not run this test longer than necessary to verify that the generator works.

If you get no output at all, I'd say it's quite possible one of the wires broke off from one of the studs when it twisted.

Check out this link for more info...
http://www.vw-resource.com/generator.html
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[Wildthings]

Did you polarize your new regulator? I don't work on these often enough anymore to remember what to do without just getting out the manual and following their troubleshooting instructions step by step.

[telford dorr]

Uh, regulators don't 'polarize' - only generators...
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[SGKent]

[telford dorr]

Nah, wouldn't worry about it - we'll all be dead from undeflected radiation as the earth's magnetic field goes through zero...
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[alman72]

i will wait the 10k years to figure that one out

[old DKP driver]

You probably broke the wire off the post inside the housing but it can be soldered back usually without removing the generator.
I did this a few times when I was a young tech. We also were in the habit of
Taking the belt off and jumping d+ to run the generator/fan to cool the engine
Down faster in order to do the valve adjustment quicker.
The worst scenario would be pulling the generator and taking it in to a repair
Shop.
_________________
V.W.owner since 1967

[SGKent]

[bnam]

I did try to polarize the dynamo. I was surprised when it turned very slowly when I connected the battery to d+ after grounding df. It did seem to slowly pick up speed but i had read not to do this for long so stopped.

Does the slow rotation during polarization give us a clue?

@old dkp driver - any how tos on soldering without removing?

Thx!
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[old DKP driver]

You should still be concerned that the connection may be broken under the
Housing.but glad to see the generator is working.
_________________
V.W.owner since 1967

[bnam]

I will also check the ground and see if it is a grounding related issue.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[SGKent]

you could look for a cheap core that is no good but cheap, and practice on it..
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[telford dorr]

[bnam]

Would resistance measurements between D+ and D- (12ohms) and between D+ and DF (16ohms) tell me anything? What should the stock readings be? I guess I could check on my bug.

I checked the ground, was good.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[telford dorr]

[aeromech]

[cab57]

bnam,

I have the same issue with my rebuilt 6v generator.

The polarization test was passed successfully, but not more than 0,5v with my drill at 1600 rpm.

I have about 3ohms between Df and D+, armature and brushes are NOS but same value (0,5v at 1600 rpm) with the original armature.

I am desapointed, everything is new or rebuilt.
_________________
Beetle convertible built 06/66
Beetle ragtop built 28/04/59

[telford dorr]

Connect a battery (or battery charger) between D+ (positive) and Df (negative) [should pull around 4 amps.] Spin the generator again and measure the voltage between D+ and the case.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[bnam]