battery discharge with aircon on

[V8Dom]

since playing with the dash, and removing the battery guage and replacing with led charge light, and replacing battery ignition light and swapping indicator light and oil warning lights to the new led warnings, ive noticed as soon as i turn aircon on batery voltage reduces and drains

my question is 2 fold.

1/ on the old fords if you had a bulb go on the battery warning light it didnt charge? is ultima wiring the same??? ie if its now led. it might give a wrong reading?

2 has anyone experianced this themselves?

dom

[Storer]

Dom

You could test by fitting a conventional bulb in line to your led. If the voltage to the battery rises you then fit a resistor to simulate a bulb.


Paul

[Steve_D]

Yes you do need either a conventional bulb or a resister in the charge light circuit.
If the alternator does not see +12v on this line it will not charge.

Steve

[F.C.]

Steve_D said:

Yes you do need either a conventional bulb or a resister in the charge light circuit.
If the alternator does not see +12v on this line it will not charge.

Steve

Interesting, I have a LED instead of a conventional bulb but my battery charges ok, the led does however glow dimly,(with engine running) which can only be seen in the dark, I know everything else is spot on as I had my alternator re-built recently (bearings) and the charging circuit was checked out.
I may have a look and see if a resistor will cure this "problem".

[Steve_D]

An LED and resistor will do the job but you loose the diagnostic aspects of using an incandescent bulb.
When you turn ignition on +12v passes through the lamp and is earthed by the alternator. When you start the engine the +12 stimulates the alt. and it starts charging putting +12 on that side of the lamp. With +12 on both sides the lamp does not light.
If the lamp glows it means the voltage at the battery and the alternator do not match which may mean the alt is not charging properly. Flickering is another clue.

Using just an LED may work with some alternators which may cope with the lower voltage. It may glow because it uses very little voltage to light so could be detecting the voltage drop in the wiring.

Steve

[F.C.]

Steve_D said:

An LED and resistor will do the job but you loose the diagnostic aspects of using an incandescent bulb.
When you turn ignition on +12v passes through the lamp and is earthed by the alternator. When you start the engine the +12 stimulates the alt. and it starts charging putting +12 on that side of the lamp. With +12 on both sides the lamp does not light.
If the lamp glows it means the voltage at the battery and the alternator do not match which may mean the alt is not charging properly. Flickering is another clue.

Using just an LED may work with some alternators which may cope with the lower voltage. It may glow because it uses very little voltage to light so could be detecting the voltage drop in the wiring.

Steve

Thanks for that, makes sense. I think I may try a resistor to see if it stops the LED glowing in the dark.

[V8Dom]

Steve_D said:

Yes you do need either a conventional bulb or a resister in the charge light circuit.
If the alternator does not see +12v on this line it will not charge.

Steve

thanks steve ... it seems only evident when i use aircon......massive drain...charging minimal without aircon on... alternator been removed and tested ok

what sort of resistor do you suggest??:::... and where...

in the led warning.... http://www.carbuildersolutions.com/uk/straight-war... which is where the old bulb used to be ....

or the led charge light that used to have a round white ultima gauge? http://www.ebay.co.uk/itm/12v-24v-LED-Battery-Leve...

thankyou... been bugging me for ages......

Edited by V8Dom on Sunday 12th July 23:50