LED alternator warning light

[david58]

Where can you get the one on top?
That was funny spell check missed it.

[Speedy Jim]

http://www.ebay.com/

Search in Toys & Hobbies for "Alf".

[chayes]

Please excuse me, but the next day I found a dead battery in my cheapie voltmeter. When I used a good meter it showed the battery was charging correctly. Sorry I asked for help too soon....
Thanx

[david58]

Please excuse me, but the next day I found a dead battery in my cheapie voltmeter. When I used a good meter it showed the battery was charging correctly. Sorry I asked for help too soon....
Thanx

We were making fun of my typo not of you. It is good you found the battery in the meter was dead. I have done the same thing it is easy to forget the meter has a battery.

[freekazoid]

You are 100% correct; the LED light will probably not allow the alternator to begin charging.....

Would this mean the alternator would have basically no output? I was thinking my alternator was dead because it was not charging my battery and if I disconnect the battery when the engine is running it dies right away. I sure would like to not have to take the alternator out if its not actually defective.

[david58]

You are 100% correct; the LED light will probably not allow the alternator to begin charging.....

Would this mean the alternator would have basically no output? I was thinking my alternator was dead because it was not charging my battery and if I disconnect the battery when the engine is running it dies right away. I sure would like to not have to take the alternator out if its not actually defective.

It will not charge without the idiot light, The LED doesn't draw enough to excite the ALT, but there is a way to use a LED to make it charge.

[david58]

You are 100% correct; the LED light will probably not allow the alternator to begin charging.

My sketch below shows how to overcome this.
The 100 Ohm resistor will pass enough current to start the alternator.
The additional diode protects the LED against reverse voltage and also prevents engine run-on which can occur, especially with any kind of electronic ignition. An ordinary 1 Amp diode (200V rating) will suffice here.

I'll assume that the LED lights you have are rated for 12V operation and have some kind of limiting resistor built-in. If not, the light will need an additional resistor in series.

Speedy Jim
http://www.nls.net/mp/volks/

[freekazoid]

It will not charge without the idiot light, The LED doesn't draw enough to excite the ALT, but there is a way to use a LED to make it charge.

I'm happy to hear that. Thanks for the info.

[loudoun90]

Jim, I'm having the same issue however I have a question regarding your diagram. Is the resister and diode unit one of the same?

[Dale M.]

Probably not..... Usually its assembled from components parts (diode and resistor) from Radio Shack along with "standard" LED dash indicator....



Dale

[r1cpowdercoating]

hey speedy, I have sorta the same problem. I have a large (3/4) alt.light. my light comes on with the key as you would expect Crank the car and the light goes out but the alt only charges about 15 amps according to my amo probe. It has just been rebuilt and they said it was in good order. Got any suggestions?

[Dale M.]

hey speedy, I have sorta the same problem. I have a large (3/4) alt.light. my light comes on with the key as you would expect Crank the car and the light goes out but the alt only charges about 15 amps according to my amo probe. It has just been rebuilt and they said it was in good order. Got any suggestions?

IF Alt charges, its not a idiot lamp problem, Alt only need to a shot of 12volt to initialize ( first couple of seconds at start up) once that happens idiot lamp only indicates charging or not.....

IF alternator only puts out 15 amp its either a problem with alternator itself, or system does not have enough "draw" to force alternator to put out higher amperage... Turn everything on electrical in car (lights- radio- whatever ) and see if alternator increases charge rate to match electrical drain...

Better test would be to check VOLTAGE across battery, fully charged (alternator working properly) you should see 13.8 to 14.4 volts across battery....

Dale

[r1cpowdercoating]

hey dale, this alt problem is in a car that I have several trick things including a killer sound system and some projector/halo head lights. It will kill the engine if I drive a ways at night. I have a lot of leds and its aggrevating not to be able to show them off. I am runnung 2 batteries and with the car running and I have #13 volts at the batteries even with everything running. With duel webers its a pain in the ass to pull the alt.

[Dale M.]

If you spin up motor to say 2000 rpm and you can not hold batteries at about 14 volts with everything turned on you have a alternator problem.... Its either to small (amperage wise) or is defective....

Standard alternator (Bosch AL82) is only good for about 55 amps (max)....

The fact alternator initializes and starts to charge indicates idiot lamp circuit is good....

You may want to test system with incandescent bulb to prove it is good and maybe problem really is with LED indicator (maybe wired wrong)...

Dale

[r1cpowdercoating]

ok got back to the '67 alt problem today. I was driving the car after dark with the headlights on, all the gauges lit and the stereo cranked up pretty good. I noticed that the alternator light was on but very dimly. Any ideas? or do I need to take it back to the people that rebuilt it and let them have the aggrevation of pulling it off and fixing it right.
ron