Right im having a few issues with my car at the minute
When starting my car im having to rev the car upto about 5k for my alternator charging light to go out but once charging and on tick over again the light doesnt come back on again.
The alternator is a brand new 70amp item, the belt is brand new also and is nice and tight.
Now someone mentioned to me, because im using an LED as my charging light it takes a lot more power to flow first before the charging system becomes active but i cant see how this is true and dont really believe it.
So could this LED be the problem to my charging and replacing it for a normal bulb fix it or do you think there is something else which may well be causing the issues?
Yes, the led is to blame, unless you have installed resistors and other fan dangled electrickery. Im no electrician but I did that also with my mini and had problems. Best off reinstalling a bulb.
> Yes, the led is to blame, unless you have installed resistors and other fan dangled electrickery. Im no electrician but I did that also with my mini and had problems. Best off reinstalling a bulb.
Ah right thanks very much Bert, was kind of thinking the alternator might of been at fault and was thinking of buying another one tomorrow and taking this one back.
You can install resistance in parallel with the LED, so long as the total resistance is the same value as the bulb should be. You will also need to use a blocking diode to protect the LED from the alternator.
im pretty sure it uses the feedback through the bulb as the ‘exciter’ for the field in the generator - if it doesnt get excited - then it doesnt charge. An led will let through much less current (and also drop the voltage) than the bulb. As above - probably best just putting a bulb back in.
As above, the LED by itself will make it nearly impossible to get the alternator field coils to energize.
The method Dan suggested (if you want to keep the LED) is the fix. Buy a large wattage resistor (1/2 Watt or larger) rated for something close to 50 Ohms. Disconnect your LED and place the 50 Ohm resistor in series with your wiring between the ignition switch and the small wire on the alternator. Now wire your LED back in. One side of your LED will connect on the ignition switch side of the 50 Ohm resistor, the other side of your LED will connect to the alternator side of the 50 Ohm resistor.
Note this carefully, your LED has a dropping resistor probably close to 1k Ohm. If you bought a commercial (off the shelf) LED lamp the LED will probably be buried inside the lamp housing. If you bought your own discrete LED to make the indicator, you had to add an external resistor. With the commercial light… just wire it up as I described above. If you installed a discrete LED with an external resistor… you MUST continue to use your external dropping resistor as you did before. The 50 Ohm 1/2 Watt resistor does not replace the LED’s dropping resistor, it just allows more current to flow to the alternator during start up.
Thanks very much for all your help guys, will get myself sorted with it, might end up keeping the LED and wire it up as in the described methods as the LED originally was put in just to get it through the ticket because the bike clock im using doesnt have an ignition light.
> Thanks very much for all your help guys, will get myself sorted with it, might end up keeping the LED and wire it up as in the described methods as the LED originally was put in just to get it through the ticket because the bike clock im using doesnt have an ignition light.
if you want a quick bodge. connect the bulb up, hide it and run the LED off it in parallel.
Which is fine until the bulb blows behind the panel and you can’t see that it’s failed. Then you have no idea that the alternator isn’t charging any more.
> Which is fine until the bulb blows behind the panel and you can’t see that it’s failed. Then you have no idea that the alternator isn’t charging any more.
only a quick bodge if you read. so its still drivable untill the problems fixed properly.
Right ive got myself my resistor today a 1/2 watt rated for 51 ohms, I shall be fitting it tomorrow, if I have any problems I shall be back to ask for some more advice
Right im wondering if you guys can help me. Ive now wired in the resistor before the LED on the ignition switch side.
Ive started the car up yet it still refuses to go out unless reved hard.
What do you suppose could be the problem?
Just to check ive wired it up correct, the resistor is wired into the ignition switch wire (all white wire) and then onto the LED, which is then connect to the brown and yellow stripped wire (alternator), this is correct isnt it?
Oh and a question for dklawson, you did mean a 1/2 watt resistor didnt you, not a 1 or a 2 watt resistor?Just checking ive not missread what you wrote.
It can be almost any decent Wattage as the resistor should only be carrying current for a short burst. 1/2 Watt minimum would be my recommendation but bigger won’t hurt.
I did not say “before” the LED. Take the LED out. Connect the resistor between the ignition switch and the small spade terminal on the alternator. With the engine off, measure the voltage across the battery. It should be about 12.5 V. Start the engine and measure the voltage across the battery again. It should have increased by at least 1V. Look for anything between 14V and 14.5V as typical.
Once you know the resistor is allowing the alternator to work, THEN wire the LED in PARALLEL to the resistor. That is to say, connect one LED lead just before the resistor, the other just after the resistor. This is not the same as what you said (“before”). When you say “before” that implies a series connection, not parallel. The connection of the LED must be parallel.
EDIT:
Sorry, the board software won’t let me do a “text” sketch showing schematically what I’m talking about.
See this link instead: http://www.tigoe.net/pcomp/img/relay-schematic.jpg
Look at the top right part of the JPG (**IGNORE EVERYTHING ELSE IN THE PICTURE**)
You’ll see a diode (Arrow head pointing at a bar) symbol.
Note how the lamp is “parallel” to the LED.
That’s what you want, your resistor represents the lamp in the JPG.
Put your indicator LED parallel to the resistor.
Ah right sorry I misunderstood what you previously said.
Ive decided to call it a night now, im too cold and wet but I will do that tomorrow night and get it all sorted out.
Thanks once again for your help
