I have a 1984 VW that the alternator is not charging the battery. I had the alternator checked and it is ok. Any ideas?

Natsmccrory
15

Asked by Natsmccrory Jun 07, 2012 at 11:44 PM about the 1984 Volkswagen Rabbit

Question type: Maintenance & Repair

16 Answers

Andrew Olsen
9,575

start simple. battery while sitting there should be close to 12.6v. While running voltage reading at battery should read 14v (at least 13v). If you find those readings i can give more advise. I dont want to just shotgun ideas out

1 out of 1 people think this is helpful.
Scott Sr.
3,475

With a vehicle that old, battery wires, terminals, and grounds are always less than optimal. Removed one end of the ground cables between the engine block and the body. Clean the end and the mount location vigorously with a wire "toothbrush". Reattach and do the same for the engine end of the cable. Check the battery cables for any signs of green corrosion leaching out from under the insulation. It would be a good investment to replace the main ground and main positive cables if any is found. Remember, there must be a good path for conduction from the positive battery terminal to the vehicle charging system and through to ground. Don't forget to have the battery tested as well. They can go bad as well.

1 out of 1 people think this is helpful.
Natsmccrory
15

I swapped batteries out of my other car. Sitting not running. 12.4. Running 11.48 reving the motor up didn't help. I have changed out the battery ends and have changed the main ground out. Is there a fuse that might be bad?

Scott Sr.
3,475

Nope...but something is definitely dragging down your voltage. Make sure you have the proper belt installed...too narrow and you can reduce the rotational speed of the alternator at the pulley. I'm beginning wonder if the alternator was tested under a proper load.

Natsmccrory
15

I took the alternater to a shop and he put it under a load. He also checked the brushes. The little wire that hooks up to the alternator should have keyed on power right? I have keyed on power, but it is really dim on the test light. Any more ideas? Thanks

1 out of 1 people think this is helpful.
Paul Pedersen
75

there needs to be a ground strap between the alt and the motor block the upper adjusting arm is on a rubber gromet and the lower mount never seems to ground very well VW put a small ground strap at the back of the alt going to the waterpump bolt its prolly corroded real bad or gone completly I usually run a big strap from the upper mount to the shock tower get stainless steel if you can. good luck

1 out of 1 people think this is helpful.
Scott Sr.
3,475

A good test is to ohm out the alternator case to ground...should be close to 0 ohms. If not, then Paul's idea is probable cause.

Natsmccrory
15

Paul the ground strap from the alt to the water pump is there. Where is the shock tower?

Natsmccrory
15

Just cleaned the ground strap from the water pump to the alternator. No difference.

Natsmccrory
15

Scott how do you ohm out the alternator?

Scott Sr.
3,475

using a multimeter...set to measure resistance (ohms)...one lead on the alternator case and one on the engine block (clean ground)....should read zero.

Hector Irizarry Duval
2,055

There was an issue on the battery cable on those years because of the material they use I think it was with aluminum but not sure. Try with a cable directly from the battery to the alternator and check the readings again. You say you swap batteries so I discard the batterie gone bad. It's definitely an alternator or wire issue

Natsmccrory
15

Thanks Hector. I ran a ground from the battery to the alternator and nothing changed. Still haven't had time to ohm the alternater. Going to try that tomorrow. How about the blue wire that hooks up to the alternater. How bright should the test light be when the key is on. It is pretty dim.

Hector Irizarry Duval
2,055

if the light in the dash is dim maybe you have a problem with the cable from the dash. it wont work if this cable is broken or has a bad connection. try this put a 12v bulb connect to 12v bat and to the alternator plug (not the battery cable) the bulb should lit up, turn the engine on and measure the volts on your battery if its good the line from the dashboard is damaged, broken or has a bad connection. check that.

Paul Pedersen
75

if the bulb in the dash is burnt out the alt wont charge either

1 out of 1 people think this is helpful.
Hector Irizarry Duval
2,055

that car has leds, i dont think it's burnt.

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