'05 3.0 not charging but no charge light?

[pentode]

Anyone happen to know offhand what the theory of operation of the charge fault light is on the 3.0? Mine's clearly not charging but no indicator light. Wife took the truck today, complained of the dash going nuts and the radio going on and off... Checked and the battery was down to 11 volts.

Put a little charge in it and it started and ran but voltage steadily dropping. Good b+ at alternator. Mainly wondering why the computer isn't complaining, I'm thinking that must be a clue to what's going on.

 

[franklin2]

There are some fuses and fusible links in the charging system. Here's the diagram for a 2005.

 

[pentode]

Thanks, that'll be super helpful!

 

[pentode]

It's the regulator. Still don't understand why there's no charge light coming on. I thought it was the PCM that turns the light on given some kind of feedback, current, voltage, whatever, but I guess there's something I'm missing.

 

[pentode]

Someone double check my circuit dyslexia here... I don't recall ever digging in to this style of regulator before. The brushes are as unevenly worn as they look, but I don't know if that's normal wear or how much travel they need.

The alternator passed the full field test (16V at idle) so... It's gonna be the brushes isn't it?

It doesn't appear they're serviceable. I might service them anyway.

 

[Jazzer]

Can’t be to bad to replace brushes. They might not be making good contact.16v at idle seems really high.

 

[Curious Hound]

New regulator should come with brushes, I'd recommend replacing regulator and brushes as a unit.

The brushes are spring-loaded. So, uneven length, in itself shouldn't be a problem unless one is so short that the springs can't push it against the commutator.

 

[pentode]

Can’t be to bad to replace brushes. They might not be making good contact.16v at idle seems really high.

16V is bypassing the regulator. Just verifying the alternator is still working. Full field current.

Upon first inspection the brushes seem to be captive in the housing (probably so they don't fall out) and the while housing seems permanently glued together. I'm sure in theory it was a $20 disposable part in 2005, but NAPA has one part number here, zero stock, $232

 

[pentode]

New regulator should come with brushes, I'd recommend replacing regulator and brushes as a unit.

The brushes are spring-loaded. So, uneven length, in itself shouldn't be a problem unless one is so short that the springs can't push it against the commutator.

I'm mainly wondering if the short one just got too short to make good contract, yes.

And as yours came in, I just posted my reasoning - $232 at Napa, no stock.

I'll have to spend the afternoon shopping around but options are limited here. Nothing on Amazon. Gotta check Rock auto

 

[pentode]

I have to go look inside the alternator housing - just looking at how these brushes sit in the regulator, there has to be enough left on them to reach the slip rings. It's possible the actual internals of the regulator are bad. I suppose I could test that on the bench too.

 

[ekrampitzjr]

I've had two cars with a charge light that didn't come on when the alternator failed. The light instead would also stay out when the other warning lights came on upon first turning on the ignition using the key. The lights are all supposed to turn on briefly then as a check to ensure they work.

Both cars were Fords. After changing the alternator, the light came on during the check cycle as it was supposed to.

So turn the key as though you were going to start the car. If the charge light doesn't come on with the rest of the lights, that is as bad a sign about the alternator as having the light come on when the vehicle is running.

 

[pentode]

I've had two cars with a charge light that didn't come on when the alternator failed. The light instead would also stay out when the other warning lights came on upon first turning on the ignition using the key. The lights are all supposed to turn on briefly then as a check to ensure they work.

Both cars were Fords. After changing the alternator, the light came on during the check cycle as it was supposed to.

So turn the key as though you were going to start the car. If the charge light doesn't come on with the rest of the lights, that is as bad a sign about the alternator as having the light come on when the vehicle is running.

I was pretty sure last night I checked that the indicator was working but it was late and I was punchy. I'll gather that as a data point anyway.

Just so you guys have a little sympathy for the Canucks, here's the cheapest part available from the local cheapo parts emporium (not Napa)

 

[pentode]

Rock auto has one part number... $94. Might be making a trip to the u-pull