Inverting Alternator Charge light

[JustCallMeOrlando]

Hey all,

Just going through one by one sorting out little niggling issues with the car. Next on the list is the charge light for the alternator.

Pretty much when I did the conversion, I just grafted the factory wiring loom onto the 1GGTE plug. The wires all matched up, even colour wise, and lo and behold the alternator was working.

Only problem is the charge light is constantly on. I've a feeling this is something to do with the fact the manual Supra dash the engine came from had a voltmeter and my car had the "idiot light".

Whats the simplest, smallest and neatest way to invert it, so it's normally off instead of normally on?

Cheers,
Nathan

[ViPeR_NiPPleX]

normally closed relay would do the trick

[JustCallMeOrlando]

This is what I was thinking. I'm after something really tiny that I can just stick on the wire.

[ViPeR_NiPPleX]

otherwise you could run a wire from the regulator on the alternator and do it properly: http://www.autoshop101.com/forms/h8.pdf

depends how the voltmeter was wired up to the system originally.... for simplicity, relay would sort it out

[river]

Hi,

I assume you mean the regulator is putting out its proper voltage and it would normally go to a voltmeter, but you're running an idiot light and therefore it's on all the time.

Well, you can change the red light to a green light.

But, it's more complicated then that. The idiot light will come on when the voltage drops below a certain value to show there is a problem with charging, but the voltmeter setup will just conenct to a gauge and it's up to you to see the charge isn't as high as it should be.

So, you'll need to set up something that will only switch on the idiot light when the voltage is less than 12volts or something like that. You can always fit a voltmeter somewhere and use that - or do you want to use the idiot light?

Using a NC relay wouldn't work properly as these devices can keep the contacts together down to 6v. If so you're alternator will need to be putting out less than 6v to trip the light. You want the light on as soon as the voltage drops below 12v. You can use a comparator circuit - but I need to check my notes before coming up with a circuit diagram etc.

seeyuzz
river

[wilbo666]

A relay should work if you simply need to invert it...but I do wounder why!

I was stuffing around with the alt in my cressida recently (which has a Volt gauge and and a battery light). I had regulator issues...

The volt gauge is independent of the Battery light (I suspect it is simply wired directly to the battery via a fuse).

The alternator should have "S", "L" and "IG" pins as well as the "B" bolt for the battery.
The "L" pin grounding is what turns on the Battery light (which the alternator should do when its output is less than the battery...).

Have other people that have put 1G-GTE's in place of 1G's had the same problem as you? Perhaps the alt circuit which controls the "L" pin is faulty yet the regulator still works?

When you put the car to IGN is the battery light off (and goes on when you start the car)? If you disconnect the alt belt does the light go off (when it was on)? (i.e. is the behaviour of the Battery light really inverse such that a relay-> inverter will fix it?!)

edit: if it is the case as river says a compatator / opamp could be used to make the correct signal.

Cheers
Wilbo

[JustCallMeOrlando]

Not sure ey. All I know is that the battery light is on all the time, but the alternator is charging fine. Quite weird. I've not actually looked closely though as there are other issues I'd been worrying about. I suspect you're right about the gauge. It is weird though!

[chris davey]

I agree with River. I would either change the light to a green one or snip that wire altogether.

When you get adaptronic, if that has a hand controller then that will be displayed and no more need for idiot light Alternatively, you could continue on your merry way until you notice the headlights dimming and becoming brighter with revs. Then you know something is wrong

[Pure_In_Sanity]

I would put a multimeter on the wire that is running to the dash at the moment.
If it has 12volts when the alternator is charging and a ground when its not, just give power to the current low side.
That way the current will flow the opposite way when not charging and the light will go out when its running ok.

Hope that makes some sense.

Cheers
-Phil

[BradW]

Is the warning light wired correctly?
You should have ignition connected to one side of the warning light and the other side connected to the "L" terminal of the alternator.
When the ignition is on and the engine is not running ( alternator not spinning ) the "L" terminal on the alternator is earthed through the voltage reg, causing the warning light to come on.
When you start the engine and the alternator starts charging, the reg puts power to the "L" terminal and turns off the warning light ( with power on both sides of the warning light it goes out ).
I have never heard of an alternator that uses a voltmeter instead of a warning light. Voltmeters are just connected between ignition and earth. The alternator uses the warning light to start it charging so normally if the warning light is not working the alternator wont charge, I have however seen alternators "self excite" or start charging without the warning light working.
Hope this helps.

[JustCallMeOrlando]

I'll have to have a look at it. Cheers for the ideas guys. All should become clear when I have time to whip out the multimeter.

[takai]

As several have said, the voltmeter works completely independently of the regulator. On the SX corollas which came with a voltmeter not a warning light, the L pin just goes off into the loom and connected to 12v.

Basically when the Alternator starts spinning it will change the voltage differential.

[JustCallMeOrlando]

I'll have a look tonight to satisfy my curiosity, perhaps the L pin is never getting power to it. Either that, or I've cocked up the wiring

Cheers for all the help, at least I know how exactly it works now.

[bansheebuzz]

either you have wired it incorrectly or there is a problem with the alternator.

L - light gives out 12v when charging and neg when not

S - battery sense requires constant battery supply direct from battery

IG - ignition requires ignition switched 12v

[rob1]

I had exactly the same problem albeit on a ra23. Found it was the ignition side of the charge light had a short. When the engine isn't running the light won't come on,when the engine is running, it will as the alt. side is only active when the alternator is spinning.

When the ignition is on but the eng is not running check if one of the two charge light inputs have 12v. If neither do then you know it's not a problem with the alternator side.