Ignition warning light on ???

[Rob Ford]

Need help here guys

Driving late the other night
Ign light came on
All lights went dim and just got home before battery drained

Next day charged battery all okay
Did test across battery and no charge while engine running only had 12.6 volts

Today fitted new alternator
Car now charging got 14.5 volts across battery when engine running

BUT Ignition light comes on 20 seconds after you start the car
As i say alternator is charging battery fine

any ideas anyone ??????

 

[Juice]

Not sure what you mean by ignition light. Got a pic?

 

[Dino Dino Bambino]

Not sure what you mean by ignition light. Got a pic?

He was probably referring to the battery warning light.

BUT Ignition light comes on 20 seconds after you start the car
As i say alternator is charging battery fine

any ideas anyone ??????

Did you disconnect the battery when you installed the new alternator? Make sure you have proper B+ and ground connections on the back of the alternator, and make sure that the B+ from the alternator is connected to the positive battery post.
You may need to disconnect the negative battery cable for a few minutes to reset the KAM. Then when you start the engine again, perform the idle relearn procedure.

 

[Rob Ford]

Yes sorry battery light
(Ign light in UK)
what is the relearn process ?

Regards

Rob

 

[Juice]

Did you check the volts after the light comes on and with the engine running?
Dino is talking about resetting any codes (battery disconnect) and then letting the car ldle so it can learn idle.

 

[07 Boss]

I've had bad alternators out of the box. Voltage can be good and the alternator still can be bad. Have to test the diodes. I do have a brand new, not rebuilt, alternator I have been keeping on the shelf as a spare. But since I have gone to the 2010 alternator I haven't had any issues.

 

[Rob Ford]

Yes checked voltage across battery with battery light on 14-3 volts at idle

 

[07 Boss]

Yes checked voltage across battery with battery light on 14-3 volts at idle

Like I said, that doesn't mean it's good. You have to test the diodes.

 

[Rob Ford]

The 3 wires that go into plug at back of alternator look very frail and brittle
They must get very hot where situated

I will test them for continuity tomorrow
The alternator must be getting 12v supply or it would not work ?

i assume the other 2 wires go to pcm ?

 

[07 Boss]

Yes, check your wires but also run a DIODE TEST. You can show good voltage BUT that does not mean it is OK.

 

[DieHarder]

Remove, clean and re-tighten all of the main battery grounds. Floating grounds will do a number on your electronics. I chased a problem for two weeks that appeared to be a bad alternator (worked, then would go low and indicate charging problem) when in fact the alternator was good. Fixed it by adding another ground from a bolt on the alternator (4 gauge wire w/lugs) to the main ground on the passenger strut tower.

Given the age and condition of some of the battery cabling looking thinking about replacing it entirely. Appears to be around $200 or so for an OEM replacement set. Anyone have any experience doing it?

 

[Pentalab]

Put your DVM across the battery terminals ( eng on, idling). I measure 14.75 vdc on my 2010 GT.
Then switch DVM to to read AC volts. With good diodes, you should be reading O vac ..or just a few mVolts of AC. IF you are measuring a lotta of AC voltage, one or more of the 6 x diodes has failed shorted. The alternator is 3 phase....and uses 6 x diodes in total.

 

[Doug Huggard]

I had the same issue at the track a while back. Turned out to be a rub through on the signal wire to the pcm from the back of the alternator, shorted to ground.

 

[Juice]

The 3 small wires on the rear of the alternator are:
Switched 12v +, needed for the field circuit.
Gen control- this is the pcm regulator function.
Gen monitor - feedback to the PCM.

 

[Rob Ford]

I am going send alternator back and get replacement
If light still on i will check all through cables

ive been told by auto sparky problem is most likely bad diode in the new alternator as that will bring the red light on

The light comes on around 20 seconds after car is started

I had no red light before the alternator failed

Thanks
Rob

 

[07 Boss]

I am going send alternator back and get replacement
If light still on i will check all through cables

ive been told by auto sparky problem is most likely bad diode in the new alternator as that will bring the red light on

The light comes on around 20 seconds after car is started

I had no red light before the alternator failed

Thanks
Rob

I've had bad alternators out of the box. Voltage can be good and the alternator still can be bad. Have to test the diodes. I do have a brand new, not rebuilt, alternator I have been keeping on the shelf as a spare. But since I have gone to the 2010 alternator I haven't had any issues.

Like I said, that doesn't mean it's good. You have to test the diodes.

Yes, check your wires but also run a DIODE TEST. You can show good voltage BUT that does not mean it is OK.