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daihatsu type alternator not charging?
NS Dev - 21/1/07 at 12:04 PM

One of the contributing factors to my injections system issues was my "recon" daihatsu alternator not charging.

Any ideas on testing it and what could be wrong?

The charge light goes off as soon as the engine starts, and all appears ok, but no charge is getting into the battery.

The main output from the alternator is wired via the starter solonoid connection to the battery, and the other two spades on the back are to ignition controlled live and charge warning light, and I guess they are the right way round as the light goes off correctly as it should!

ideas?

NS Dev - 21/1/07 at 12:18 PM

one penny that is trying to drop is that I have used LEDS for all my warning lights.

I assumed this would be ok as I thought the ign live connection on the alternator was the exciter.

Have now read that it is just a feed for the reg and that the excite comes via the warning lamp, do if its an LED that might not work??

(Though the lamp is going off when the engine is running and comes on if it stalls etc)

omega 24 v6 - 21/1/07 at 12:30 PM

I seem to remember from my dark and distant past that the alternator warning light had to be of a certain wattage (3 watts I think) in order for the feild to excite enough for charging. It'd be worth a try and quite easy to do.

BenB - 21/1/07 at 12:36 PM

Often you do need a fairly low resistance (ie high power bulb) in order to get the field flowing. On my ST I mucked around for ages trying different bulbs, resistors etc. In the end I just bridged the connection (ie zero resistance) and it's worked fine since....

iank - 21/1/07 at 01:03 PM

If you check out the circuit diagram for bright 6 the ignition LED also has an associated diode and resistor (no values given unfortunately) to give the excitation.

http://www.lightninglooms.co.uk/bright6%20instructions%201_1.doc

02GF74 - 22/1/07 at 05:52 PM

quote:
Originally posted by omega 24 v6
I seem to remember from my dark and distant past that the alternator warning light had to be of a certain wattage (3 watts I think) in order for the feild to excite enough for charging. It'd be worth a try and quite easy to do.


worth a try but there should be some residual magentism to allow it to self-excite - the field curent via the bulb helps it along its way, usaully ....

have you put a dvm on the output of the alternator/across battery when it is running?

NS Dev - 22/1/07 at 10:56 PM

put a meter across the battery and the voltage is 12.5 volts or so and dropping as the engine is idling, dropped about 0.4v in 2 mins so deffo not the 14.4 ish volts it should be seeing!

tks - 23/1/07 at 07:24 PM

its deffo the field in fact you activate the regulator.. the fact that it connects battery to that bulb is to say the dyno bulb works in that way you know when it charges and that the bulb is ok at startup.

measure a bulb look at its resistance..
calc its wattage extract the leds.. and you should be able to make it work easly..

i would just source a bulb and try it first with that..then start experimenting with the leds..

i don't think that the alternator needs this bulb to work, it could be true but in theorie then the bulb should iluminate
or the amps passed thru are low.
shorting it to ground certainly isn't the solution because then the internal circuitry will burn out and you won't know when you don't have a charging dyno on..

i guess that the bulb is connected to battery when dyno off (or internal error) and in series with field when in ok status.

the field current needs to be less when the dyno turns faster in order to regulate to the given 14,4volts...

anyway try with a bulb from their on you mockup a resistor with a transistor and a led in that way you switch the led with battery power and it won't burnout depending on revs. (i guess)


Tks