74 Super Beetle charge light on but its charging

Moderators: Sluggo, Amskeptic

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Mon Feb 25, 2013 1:22 pm

Motorola alternator w external regulator. The system appears to be charging fine i.e. running car shows 13.8 volts at b+ terminal and at battery positive. The problem is the charge light in the dash is on very bright. What should I be looking for?

The light would come on brightly with the ignition, then goes dimmer after the engine starts. The diff in voltage between b+ and D+ is about 1.8 volts with the engine running. This is the voltage that appears to be lighting the bulb. Where should I look to for the bad connection?
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super beetle charge light on but its charging

Post by Amskeptic » Mon Feb 25, 2013 2:02 pm

RSorak 71Westy wrote:Motorola alternator w external regulator. The system appears to be charging fine i.e. running car shows 13.8 volts at b+ terminal and at battery positive. The problem is the charge light in the dash is on very bright. What should I be looking for?

The light would come on brightly with the ignition, then goes dimmer after the engine starts. The diff in voltage between b+ and D+ is about 1.8 volts with the engine running. This is the voltage that appears to be lighting the bulb. Where should I look to for the bad connection?
Go back to the battery positive with engine off. Read voltage. Start engine. Read voltage.

Go to center wire of alt idiot light (blue). Pull it cleanly off terminal, small spade, careful. Idiot light will go out.
Read voltage on wire against any good ground.
Shut off engine.
Read voltage off that same wire. Should be "0" volts.
NOW:
Ignition on, no engine.
Put red (+) of tester on base plate where plastic terminal is pressed-and-turned in. Ground the black (-) wire of tester on known ground metal. Read voltage.
Git back to us.
Revert everything to as it was.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super beetle charge light on but its charging

Post by RSorak 71Westy » Mon Feb 25, 2013 2:41 pm

Go back to the battery positive with engine off. Read voltage. Start engine. Read voltage.
11.2 Low I know, running 13.8 and rising

I can't get to the center wire of the idiot light. The back of the dash in this VW is not accessible at all. Any advise on this count?
The trunk is useless for gettin to the dash. The idiot light in question is directly over the steering column, thus its blocking all access to the back of the dash.

I did find the blue wire at the regulator plug.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
dtrumbo
IAC Addict!
Location: Mill Creek, WA
Status: Offline

Re: 74 Super beetle charge light on but its charging

Post by dtrumbo » Mon Feb 25, 2013 4:07 pm

RSorak 71Westy wrote:The back of the dash in this VW is not accessible at all. Any advise on this count?
If the '74 is like my '79, use your best Spider-Man finger tip grip and pull the speedometer (and thus all the idiot lights) straight out of the dash. You will need to disconnect the speedometer cable first, however. In my '79 I can reach through the clock hole (after Spider-man'ing the clock out of the dash) to disconnect the cable. I've never worked on any other Beetle other than my own so I have no idea if the above suggestions will work in your case, but hopefully you'll find it useful.

Good luck.
- Dick

1970 Transporter. 2015cc, dual Weber IDF 40's
1978 Riviera Camper. Bone stock GE 2.0L F.I.
1979 Super Beetle convertible.

... as it turns out, it was the coil!

User avatar
hambone
Post-Industrial Non-Secular Mennonite
Location: Portland, Ore.
Status: Offline

Re: 74 Super beetle charge light on but its charging

Post by hambone » Tue Feb 26, 2013 11:36 am

Why are you working in the front of the Bus for these tests? I've always worked in the engine compartment only. What are you testing for with this method? Can't you just isolate the generator and see if it's producing? As you know electrical stuff is confusing to me.
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
your brand new leopard skin pillbox hat

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super beetle charge light on but its charging

Post by Amskeptic » Tue Feb 26, 2013 8:14 pm

hambone wrote:Why are you working in the front of the Bus for these tests? I've always worked in the engine compartment only. What are you testing for with this method? Can't you just isolate the generator and see if it's producing? As you know electrical stuff is confusing to me.
This is a Super Beetle! With a Motorola alternator!

We need to see where the imbalance of electricity is, because he said "the charging system is working". The idiot light has 12 volts coming to it from the base plate, fed by the ignition switch voltage, and the alternator sends 12 volts up the wire to put the light out. Somewhere he has either an inadvertent ground or an open circuit, and we need to know which side of the light is the problem.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Thu Feb 28, 2013 12:44 pm

The speedo is NOT pulling outta the dash. I've hooked a bent pick under the edge and pulled as hard as I dared in a couple of different spots and the speedo didn't even begin to move. I can only access it from the bottom as the top 4/5 ths is surrounded by the padded dash.

How else can I make this gen light go out?

If I cut the blue wire at the back I can perform the next test.

How can I perform the last test, without access to the back of the dash?
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by Amskeptic » Thu Feb 28, 2013 3:58 pm

RSorak 71Westy wrote:The speedo is NOT pulling outta the dash.
How can I perform the last test, without access to the back of the dash?
OK, let's try accessing the blue wire from the engine compartment side as though you were pulling the engine out. There should be a rectangular amber connector. Disconnect it.

A)
Put your tester (+) on the regulator side of that blue wire connector-that-is-no-longer-connected to the wire leading to the dash.
and your tester (-) on any piece of grounded metal.

Engine OFF, there should be no voltage.
Engine ON, there should be 12 volts.

IF NO VOLTAGE, check regulator red/blue terminal in the plug

B)
Ignition ON engine OFF
Tester (-) to any ground.
Tester (+) to the blue wire leading to the dash.
Should have 12 volts.

IF NO VOLTAGE, check for voltage to instrument cluster via Bentley manual wiring diagram! Fuse #12?

Confused?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Mon Mar 04, 2013 1:38 pm

OK, let's try accessing the blue wire from the engine compartment side as though you were pulling the engine out. There should be a rectangular amber connector. Disconnect it.

A)
Put your tester (+) on the regulator side of that blue wire connector-that-is-no-longer-connected to the wire leading to the dash.
and your tester (-) on any piece of grounded metal.

Engine OFF, there should be no voltage.
Engine ON, there should be 12 volts.
The blue wire stops at the regulator which is under the rear seat. I performed these tests at the reg. plug where the blue wire is crimped in the connector with the red wire. The regulator was unplugged. I unplugged the plug at the alternator, this made no diff in the results. There are 3 small wires red, green and brown that goto the alt.

Enigine off- 0V
ignition on- Battery voltage minus .4V
B)
Ignition ON engine OFF
Tester (-) to any ground.
Tester (+) to the blue wire leading to the dash.
Should have 12 volts.

IF NO VOLTAGE, check for voltage to instrument cluster via Bentley manual wiring diagram! Fuse #12?
Yes battery voltage.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by Amskeptic » Tue Mar 05, 2013 11:48 am

RSorak 71Westy wrote:
Put your tester (+) on the regulator side of blue wire
and your tester (-) on any piece of grounded metal.

Engine OFF, there should be no voltage.
Engine ON, there should be 12 volts.
The blue wire stops at the regulator which is under the rear seat. I performed these tests at the reg. plug where the blue wire is crimped in the connector with the red wire. The regulator was unplugged. I unplugged the plug at the alternator.

Engine off- 0V
ignition on- Battery voltage minus .4V
Alternator has to be plugged in. Engine *has to be running*. Regulator *has to be plugged in*. We have to test that blue wire with the engine running AND disconnected from idiot light.
Are we back to Square One?
There is no connector in the blue wire to the idiot light that we can unplug?

RSorak 71Westy wrote:
B)
Ignition ON engine OFF
Tester (-) to any ground.
Tester (+) to the blue wire leading to the dash.
Should have 12 volts.
Yes battery voltage.
Good, power through idiot light from ignition side!
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Tue Mar 05, 2013 2:20 pm

After cutting the blue wire at the alt plug, I get 11.05 on the reg side of the cut , and 13.2 on the bulb side. This is with everything else hooked up and engine running.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by Amskeptic » Tue Mar 05, 2013 5:31 pm

RSorak 71Westy wrote:After cutting the blue wire at the alt plug, I get 11.05 on the reg side of the cut , and 13.2 on the bulb side. This is with everything else hooked up and engine running.
If the bulb side of your cut, after coming from the battery>ignition switch> back of dash cluster> bulb filament>blue wire is13 volts, the aforementioned parts are good.

The regulator side of your cut is coming directly from the alternator via the red wire (D+).

Reconnect your break and apply *battery voltage from a careful jumper wire to the alternator D+ while engine is running and see if your idiot light goes out.
If it stays out when you remove the jumper, regulator is not switching correctly. Do not blame the regulator for this. It could be a lousy alternator, a blown excitor diode . . . test the regulator cut-in by removing your jumper and revving the engine to 3,000 rpm to see if that convinces the light to go out.

If the idiot light goes back on the instant you remove the jumper wire, my guess is that you have a blown diode in the excitor circuit. It does not kill the alternator output, but it does diminish it under load.
Colin
(p.s. make sure B+ is secure at alternator 10mm nut and is clean and beautiful on starter post under the 13mm nut clean and secure only with battery negative terminal disconnected, but you knew that)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Tue Mar 05, 2013 7:26 pm

Ah so a bad diode is probably the cause here. The engine has to be revved up after starting to get the system to charge. Will try your jumper wire test tomm. Thanks for all the help on this.

Took Alt off the car today and took it to the rebuild shop. Should have it back tomm.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
RSorak 71Westy
IAC Addict!
Location: Memphis, TN
Contact:
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by RSorak 71Westy » Tue Mar 12, 2013 1:44 pm

I'm so pissed ATM I could scream. After waiting 4 days for the alternator shop they finally called and said come get it nothing wrong no charge.

When getting there I ask if its normal to have to rev the engine to get it to start charging and he says no. Suggests replacing the regulator?

After all this diagnosis? This is BS. Whats going on? I hate electrical problems for just this reason, do all the tests come to a conclusion and its wrong.

Colin do you think this could be the regulator? It appears to regulate fine.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: 74 Super Beetle charge light on but its charging

Post by Amskeptic » Tue Mar 12, 2013 3:51 pm

RSorak 71Westy wrote:I'm so pissed ATM I could scream. After waiting 4 days for the alternator shop they finally called and said come get it nothing wrong no charge.

When getting there I ask if its normal to have to rev the engine to get it to start charging and he says no. Suggests replacing the regulator?

After all this diagnosis? This is BS. Whats going on? I hate electrical problems for just this reason, do all the tests come to a conclusion and its wrong.

Colin do you think this could be the regulator? It appears to regulate fine.
I have been through this. (second link was the discovery)

May 17, 2005
http://www.thesamba.com/vw/forum/viewto ... ator+short

May 18, 2005
http://www.thesamba.com/vw/forum/viewto ... ator+short


I have been through the "replace the regulator" trip. I did. Twice in a matter of days.

It was a bad excitor diode.

symptoms: need very high rpms to make warning light go out
test at shop: your alternator is fine
next symptom: light goes on when ignition goes off!!
rotor was grounding out against end plate.
Ratwell's Reply
Posted: Wed May 18, 2005 9:00 pm
Post subject: Re: That Was Interesting Part II
Amskeptic wrote:
HOW does the damn thing ground itself "at the alternator" huh? HUH? Slip rings to rotor. Rotor windings to slip ring. Bizarre behavior with alternator out of the loop. Solid state regulator that doesn't let you look inside

You just need a VOM to measure the terminals. That works for both styles.

Quote:
But I challenge anyone here to explain to me HOW the ground is effected at the rotor, and how it is stopped once the field windings are excited. Senor Ratwell, give it a crack? You will acknowleged in the text with a framed photograph next to the description

Throw away your concept of the engine being the ground and think in terms of electron flow. Remembering that electrons flow from a negative source to another that is less negative and studying the diagram backwards it sometimes makes more sense because the various "grounds" can be confusing. I was hung up on the fact that the ignition spark was negative until I started to think this way.

The VR controls the amount of field current in the rotor. When there is no field, there is no voltage in the stator. That stator voltage appears at D+ on the VR and relative to B+ on the battery lights the bulb or not.

The diodes are the magic that keep D+ at "ground" when the alternator isn't working.

The internal workings of the alternator are already well described here if you want to read more:

http://www.netlink.net/mp/volks/schem/mot_alt.htm

My only concern here is that your current Motorola may different than my old Bosch.
A spare regulator is a fine thing. I got a solid-state little junker from AutoZone for $13.99. Worked fine on the Road Warrior, less lights brightening and dimming spookily.
Colin
(p.s idiot light is not a LED super-bright replacement bulb is it? They do not draw enough current to switch the excitor diodes)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

Post Reply