Alternator not charging

[northeast dmc]

Hello, it has been a while since posting. I have made progress since my last post. I have the brakes all done, wheels powder coated and new rubber on.The car starts every time, still a slight issue with exceleration. But the reason for posting, is during the getting it to start trial and error over the last year, I knew the alternator wasnt gnerating, but wasnt a concern. It is new. The plug that came with it, had 2 wires, and the plug and connectors melted when it was hooked up. Fast forward to this weekend. I didnt get a plug but picked up connectors that would hook up to the prongs on the alternator. Using the location form the plug, I hooked up one wire to the bigger terminal, assuming this is the exciter one. Connected the wire to the hot wire in the wirind harness. Started the cran and voila the alternator gauge moved over 13 to maybe 14 volts the lights perked up and then the gauge returned to its normal reading of where the battery is and no more charging. The battery is brand new, and as i said the car fires right up. I recall the alternator charging for a short time last time as I could here it working, but qas I said it was for a very short duration. I didnt hook the second wire as I believe it goes to the gauge???

[Jonathan]

Does your battery warning light in the instrument cluster work? It must work or the alternator will not. And the bulb can’t be an LED. It must be the old fashioned incandescent. Test the warning light by turning the key to accessories but don’t start the engine. You must see that light come on to allow the alternator to charge.

[Ron]

+1

The large brown wires go on the main terminal. They have 12V at all times.
The small brown wire with a yellow tracer/stripe goes to the terminal marked "L" (Light) or "F" (Field). It has 12V when the key is in the "Run" position.
The small solid brown wire goes to the remaining terminal on original units. It has 12V when the key is in the "Run" position. It is usually not needed on rebuilt or replacement units...
Most auto parts can test the unit if you pull it off (FREE).

[northeast dmc]

Does your battery warning light in the instrument cluster work? It must work or the alternator will not. And the bulb can’t be an LED. It must be the old fashioned incandescent. Test the warning light by turning the key to accessories but don’t start the engine. You must see that light come on to allow the alternator to charge.

Thank you, I never noticed but the battery light does NOT come on, is it likely bad bulb or could there be another cause? And is it neccesary to remove the dash to change the bulb?? Thank you for the help.

[bytes311]

I had a similar problem where the battery bulb wouldn't come on with the key in the "run" position. It turned out to be a faulty voltage regulator on the alternator.

[Ron]

+1

No Battery Light is usually: Alternator's Internal Regulator or Rotor, Bulb, Fuse #5 (oil, brake, etc lights will not work either), Brown/Yellow wire (12V), wiring.
The bulb can be changed w/o removing the dash by someone with small nimble hands, but very difficult.

[David T]

That light can fail to light during start-up for a few reasons;
Faulty wiring/bad connection to the flexible circuit board in the binnacle
Burnt out bulb
Damaged/burnt wiring to the alternator
Defective voltage regulator in the alternator
First thing to do would be to test the wiring and bulb. Disconnect the N/Y (brown/yellow) wire going to the alternator and ground it. Turn the key to the run position. If the light does not light up trace it back to the binnacle and test it there till you find the problem. If the light does work, pull the alternator and have it tested.

[Ron]

+1 !

FWIW- Check the light for a faint glow, including when the key is off...

[northeast dmc]

That light can fail to light during start-up for a few reasons;
Faulty wiring/bad connection to the flexible circuit board in the binnacle
Burnt out bulb
Damaged/burnt wiring to the alternator
Defective voltage regulator in the alternator
First thing to do would be to test the wiring and bulb. Disconnect the N/Y (brown/yellow) wire going to the alternator and ground it. Turn the key to the run position. If the light does not light up trace it back to the binnacle and test it there till you find the problem. If the light does work, pull the alternator and have it tested.

Thank you for responding I bit the bullet and pulled the binnacle, and sure enough bad bulb, also when I reconnected the main plug my tach now reads correct. Put new bulb in and alternator works.

[northeast dmc]

+1 !

FWIW- Check the light for a faint glow, including when the key is off...

Bad bulb, thanks. might consider changing the other bulbs while it is out to LED.

[David T]

If you don't change to LED (and IMHO it isn't necessary) at least replace all the bulbs so you don't have to take the binnacle out again anytime soon.

[northeast dmc]

If you don't change to LED (and IMHO it isn't necessary) at least replace all the bulbs so you don't have to take the binnacle out again anytime soon.

I was wondering about changing to LED, I will just replace the bulbs and put it back in, thanks.

[northeast dmc]

I was wondering about changing to LED, I will just replace the bulbs and put it back in, thanks.

Regarding the alternator not charging, I went back in to make sure I had the correct bulb as the ones I had on hand where for the door lights, differnt part number, so I stopped and bought the 161 put it in and the battery light still comes on and no charging. Is there any thing else I can check that might cause the alternator to not charge? I have had a couple of brief indications of charging but that is all.

[dmcnc]

No that you have the correct bulb in the dash - put the key on Run (without starting engine) and test the brown/yellow wire going to the alternator with a multimeter - you should be getting 12V.




Regarding the alternator not charging, I went back in to make sure I had the correct bulb as the ones I had on hand where for the door lights, differnt part number, so I stopped and bought the 161 put it in and the battery light still comes on and no charging. Is there any thing else I can check that might cause the alternator to not charge? I have had a couple of brief indications of charging but that is all.

[David T]

If the belt is spinning the alternator and the light is on, it's time to take the alternator to a shop to get it rebuilt.

[northeast dmc]

No that you have the correct bulb in the dash - put the key on Run (without starting engine) and test the brown/yellow wire going to the alternator with a multimeter - you should be getting 12V.

The alternator is/was new when I put the motor in, I checked the voltage at the brown /yellow wire with key on,not running and with the wire connected to the alternator I read about 1.2 volts, I unhook the wire form the alternator and it goes to what the battery voltage is at, 12 volts plus minus depending on how long since I charged it. I do seem to have something drawing juice when the car is off. I am going to disconnect the battery tonight to see if battery holds charge or if the battery is bad. Brand new a month ago.

[Ron]

If the battery is bad, but good enough to start the engine after a charge, the light should still go out and the alternator should raise it to 13.5V or more. So, I'm with David -- Pull the alternator and get it tested/repaired.

[northeast dmc]

+1

The large brown wires go on the main terminal. They have 12V at all times.
The small brown wire with a yellow tracer/stripe goes to the terminal marked "L" (Light) or "F" (Field). It has 12V when the key is in the "Run" position.
The small solid brown wire goes to the remaining terminal on original units. It has 12V when the key is in the "Run" position. It is usually not needed on rebuilt or replacement units...
Most auto parts can test the unit if you pull it off (FREE).

Well back to the alternator again. Well pulled it out and decided to try it on the bench, put it the vise, hooked the multi meter up to the out put post and ground to the vise. Took my portable battery jumper hooked up ground to the vise, and with a nail in the positive applied to the differnet terminals in the plug in area. (there are 4 prongs) no description on the alternator for the prongs. And with me turning the pulley with a impact would find the terminal that would "engage" the alternator and put out around 14 volts. Install in car and nothing.

[Ron]

Well back to the alternator again. Well pulled it out and decided to try it on the bench, put it the vise, hooked the multi meter up to the out put post and ground to the vise. Took my portable battery jumper hooked up ground to the vise, and with a nail in the positive applied to the differnet terminals in the plug in area. (there are 4 prongs) no description on the alternator for the prongs. And with me turning the pulley with a impact would find the terminal that would "engage" the alternator and put out around 14 volts. Install in car and nothing.Assuming you also put the battery jumper's positive wire on the main alternator terminal since it put out... If so, it should work on the car if your small brown with yellow trace wire measures 12V (disconnected) and you put it on the same terminal that you put the nail on to make it output ~14V. (The others in the socket are not needed.)
Be careful -- Those regulators are not very forgiving if you apply ground or power to the wrong one...

Are auto parts tests unavailable there?

Post a pic or two of the alternator?

[David T]

Not really a definitive way to bench test the alternator. You really should put a load on it. You could have bad diodes or a faulty regulator. If the alternator does test good you could have a wiring problem and/or a bad battery. Get the alternator properly bench tested and have the battery checked. If they are both good you have a wiring problem in the car.

[northeast dmc]

Thanks for the feed back, I gave in and took it to the shop a half hour away and had him go through. In talking with him as was said in the post likely screwed up the regulator. So in couple days I should be in business with regard to the alternator.