Alternator Wiring question

[error_505]

4.3 v6

On my Alternator, there is a red wire (voltage regulater I presume) with a plug on it. It never seems to be hot. My volts while running is like 12.3 and my battery is never charged. I almost have to boost it every day or so.

My question is...... When should this wire be hot. I think it an energizer wire but Im not certain. I jumped 12 volts from the battery to the the red wire and my volts went to 14.3.

Im thining this is my problem but I really dont know where to start to check it. Thanks in advance for any help.

[MT-2500]

The small red wire?

Check RDO battery fuse no 19.
It feeds battery dash light and on into pcm and then to the small red wire to start alt charging.
After the alt starts charging i think the voltage from the battery dash light shuts off.
Does the dash light battery light come on key on and or engine running?
MT

[error_505]

Yes it is a RED wire in the plug for the alternator. Like a 10-8 gauge for the back side. It is red also.
The dash light comes on when in run position. Goes off when truck is running

Here is some results from testing.......

Key off
Battery 11.75v
Alternator Big red wire 11.75v
Alternator small red wire 0v

Key On
Battery 14.3v
Alternator Big Red Wire 14.3v
Alternator Small wire .813mV

As I see, its all fine and tests normal.....BUT.......Yesterday when the truck was running, Alternator reading was 11.8v and battery was the same. I jumped the LITTLE red wire from the battery and the voltage on the Alternator went up to 14.7v. After testing this morning starting with battery 11.8v. 10 minutes went by with headlights off and the battery was dead- (9.5v). A quick charge and all is looking normal, until later this evening.....lol

It seems to be random that the voltage regulator gets power or not.

[MT-2500]

Originally Posted by error_505

Yes it is a RED wire in the plug for the alternator. Like a 10-8 gauge for the back side. It is red also.
The dash light comes on when in run position. Goes off when truck is running

Here is some results from testing.......

Key off
Battery 11.75v
Alternator Big red wire 11.75v
Alternator small red wire 0v

Key On
Battery 14.3v
Alternator Big Red Wire 14.3v
Alternator Small wire .813mV

As I see, its all fine and tests normal.....BUT.......Yesterday when the truck was running, Alternator reading was 11.8v and battery was the same. I jumped the LITTLE red wire from the battery and the voltage on the Alternator went up to 14.7v. After testing this morning starting with battery 11.8v. 10 minutes went by with headlights off and the battery was dead- (9.5v). A quick charge and all is looking normal, until later this evening.....lol

It seems to be random that the voltage regulator gets power or not.

The alt should get a voltage feed threw the dash light bulb when engine starts to start the alt charging.

It is not a full 12 volt feed as it has to go threw the dash light bulb and pcm.
It could be losing it in solid state dash or pcm.
Unplug alt and take a old bulb type test light and see if the red wire is getting a feed or enough to light bulb test light or dim feed.


To test alt take the test light and hook the test light wire to positive battery and touch the test light to back of alt small wire with engine running.
The test light should come on and go out when alternator starts charging.

[MT-2500]

The alt small red wire is actually the ground for the alt dash light.
If bulb comes on key on it is grounding.
Also To check unplug alt and see if dash light goes off.
When engine is started and alt is energized by the ground side of dash light the alternator should start charging and break the ground for the alt light.
And turn off dash light.
Good luck
MT

[error_505]

The bulb test light will not light at all at any time. The dash light comes on even if the plug is unplugged from the alt. Then turns off after a second or two.

I can start my truck and it will read about 12v on alt and battery. I can rev the engine a lil and it starts to charge at 13.9-14.6v. Even with engine at idle after I rev it for the 1st time. Restart the truck and it might do the same or work correctly.

i hope Im telling you enuf info. Im losing brain cells with this one....lol

[MT-2500]

Something hay wire on the battery dash light circuit.
It should not come on unless the plug is on alternator.
The alt is the ground circuit for the alt dash light.
Open the wiring pdf and trace the wiring from dah light to alternater.

[error_505]

I removed my cluster and checked the soldering points on the Bat light. It was hot on both sides when the key was on. Only one side fed from the orange wire in the harness. Fuse #19 is hot all time. I tried to check resistance on all of them but im not sure if i did it right. I got 0.0 readings on a couple and very lil on others.
I unplugged the wire from the battery and the dash battery light does come on even unplugged. It goes off about 3 seconds just like if it were hooked up.

Im at a lose here. I really am out of my element here. Im trying and thanks for the help!!!!

[MT-2500]

Look the wiring diagrams over good.
I think the alt dash light ground also runs threw the computer before it gets to the alt.
MT

[error_505]

Well I have looked and tested and done all I know to do..........BUT......Im not having a problem now. I unplugged my radar detector and my battery has not went down and my truck starts everytime. KNOCK ON WOOD. I dont know if that was the problem but im not plugging it back up.....lol

[MT-2500]

You are welcome.
Thanks foe posting back and good luck.
MT