[SOLVED] I've missed something, Alternator not charging my battery

I know this has been discussed multiple times before (been reading for hours) but I could really use some step by step support with this one

Basically my alternator isnt charging the battery, the battery is less that 12 months old and the alternator less than 4 hours old (fml wasted money me thinks)

Leaves me to think there is a fuse/wire/voltage regulator issue (i have no idea now)

In the lead up to this I would get the battery light displaying on my dash just after startup 50% of the time (disappearing with revs) this has happened for a few months but didnt cause any other issues
Now the battery runs flat

Really need some constant support on this as im too egotistical to just palm it off to an auto sparky and pay through the nose

I had a slipping belt that did this. I'm fairly certain the regulator is in the alternator in the D22, so let's assume that it's good. Pop the bonnet and look at the pulley as the engine is idling, you should see the pulley stall (if the belt is loose) when the headlights are switched on (needs a helper).

Can you measure the voltage when the engine is idling across the battery terminals? If it's below 12.8V you've got a problem. You should see somewhere from 14.1V up to 14.7V.

Voltage on battery is 11.1V now at idle (alt Volts matches battery when measured from the + outlet to the alt earth on the body)
didnt see any slipping from the belt on the pulley either just then

Had same problem in my ute recently and I changed the alternator and all is good now. Guess that doesn't help you much. All the best with it.

have you changed any dash bulbs (in particular the alternator light bulb) ?
eg fitted LED bulbs, changed blown bulb

several weeks ago i installed a new head unit and speakers and 6 months ago a bulb for the ac display but nothing else other than that

i might add also that my meter fuse blows when i put the car into reverse (im pretty sure these are separate issues, even though they came about around the same time)
it happened after washing my car the weekend before last but its not like i washed the inside of my engine bay

my understanding is the reverse light is supplied by the meter fuse (the one that does warning lights and gauges on the dash) and i think thats related to the new headunit as it also has reverse camera capabilities that senses the power from the reverse light in order to power the camera. So i think its separate... maybe?

the car is un-useable until i can sort out the alternator issue though

It sounds like it might be alternator-related but you'd hope a new unit would actually work. There is a large pole on the back of the alternator - it should read 14+V while the engine is running, could you test that?

Head unit install + related problems: often the head unit earth (which is shared with the instrument cluster) is unreliable and causes intemittent issues. Run a separate earth to the head unit and see if that helps - power will start to flow "normally" and may rectify the issues there.

Reverse light issues in the past have been attributed to faults in the trailer connector and in the tail light assembly, both are worth checking.

i assume you mean this pole? (the red one on top)

if yes i was getting 11.1V (same as battery reading) This is the brand new alternator in the car now

definitely no output from the new alternator then!

The Likely solution!!!

Been doing research into the actually operation of an alternator and i have come across something called excitation
While i still don't fully understand the term it sounds like the the process is the warning light on your dash is actually required to firstly turn on and then turn off shortly after the car starts.
It's then after it turns off that the alternator begins to output charge.

The term is excitation if anyone wants to tidy up my rough explaination

The reason this is the likely cause is because my other issue (mentioned earlier) is actually the cause and the alternator is just a symptom

As my warning lights are currently on the fritz due to a fuse continuously blowing the alternator is getting the signal to start supplying charge.
The fuse is blowing every time I'm putting the car into reverse so now I'm on the hunt for a short

Thanks heaps to everyone who took the time to respond to this thread. Will post updates if people are interested?

Mattyd22 said:

The term is excitation if anyone wants to tidy up my rough explaination

The reason this is the likely cause is because my other issue (mentioned earlier) is actually the cause and the alternator is just a symptom

As my warning lights are currently on the fritz due to a fuse continuously blowing the alternator is getting the signal to start supplying charge.
The fuse is blowing every time I'm putting the car into reverse so now I'm on the hunt for a short

Thanks heaps to everyone who took the time to respond to this thread. Will post updates if people are interested?

Click to expand...

your right on the money.
i just had to go look in the manual. feed for the alt runs off the warning light circuits. so does the reverse lamps.
check for short between reversing switch on the gearbox and the lamps. don't forget the trailer connector as that may also be wired with a reverse connection.

If you have a reverse camera connected to your new head unit, double check the wire you have used for the reverse sense is the correct one. It may be going to a dead short and causing your issue.

The alternator bulb on the dash goes to the sense terminal on the dash, which unless it sees 12v+ on both ends won't excite the alternator to start it charging. The light only comes on before the engine is started because it is fed ignition voltage in the "on" position and grounds through the alternator until the engine starts and goes out when the alternator puts charge back into the other end of the light, turning it off.

Sent from my SM-G900I using Tapatalk

The new head unit i put in seemed to have pinched a wire as i mounted it by the looks of it
didnt find the exact spot but after checking solders and doing a little reorganising i no longer have the fuse blowing to my meters and warning lights in reverse and the battery light turns off straight after the car starts, and the alternator is charging

Happy days!!

excellent. thanks for letting us know the outcome

Great bit of detective work. Well done