New ALH alternator slow to start charging

2003 Jetta Wagon. I replaced the alternator in this car three weeks and it has worked great. I used a rebuilt unit from Autozone. (lifetime warranty)


Recently it has started taking 6 seconds for the red charging light to go out in the cluster. I checked my other car and it took .2 seconds to go out.


I checked the voltage and it stays at 12 volts until that light goes out and then it jumps to 14+ volts.


I assume this means the alternator clutch is taking a while to engage? I should get Autozone to give me a new alternator, since this one could be on the way out?

Sounds like a slow regulator in the alternator.

Autozone's lifetime warranty means a lifetime of replacing it, until you wise up and put a proper Bosch reman unit on there.

I've never seen the red light after the engine starts on either of my TDIs. If it goes off after x, your battery stays charged, you're proly fine. I would check the belt doesn't hang or flop or something when it first starts.

Yup you need another alternator. I put an auto zone starter in my tdi replaced it three times before I wised up, get a Bosch as oilhammer suggests.

I'd rather have a Bosch from the salvage yard before an AutoZone anything, both my jettas have salvage yard alternators because the one way died and I couldn't wait for a replacement, now I have spares...

Sent from my Pixel XL using Tapatalk

Thanks guys. I knew I was going to hear it about Autozone.



I like lifetime warranties though. It is a rebuilt Hitachi 120 AMP alternator which was original equipment on these cars. I do have lifetime warranty Autozone starters on a couple of my vehicles and they are still going strong after many years. I also have a Autozone A/C compressor on my sedan and it has been going strong for 6 months. So I don't think Autozone stuff is all bad.



My thought was that if you guys think it is the alternator's clutch, then I could just replace the clutch, so I don't have to pull the alternator.


Is it the clutch?



I doubt it is the voltage regulator since it puts out correct voltage after 6 seconds. The voltage would be too high to start if the regulator wasn't working. I checked the belt tension and it seem fine.

If it were the clutch it'd either be too soft and burn up quickly, or it's stuck solid and it'll throw your belt. Either way I doubt it's the clutch.

Not necessarily, I had one that was intermittent but it wasn't doing what the op states.

Mine would charge most of the time but would shudder out if the blue and the lights would dim for a second and on my other Jetta, it was spinning but not fast enough to charge, sprayed some pb blaster on it and it seemed to work good after but I didn't swap it to find out

Sent from my Pixel XL using Tapatalk

A bad alternator takes a toll on the battery; a bad battery takes a toll on the alternator.
It's best to make sure both are in tip-top shape.

I have a new H8 battery in the car. I just checked it with a battery tester and it is in perfect shape.


Wildchild, did you spray PB Blaster on the alternator pulley/clutch? I could try that.

Best idea is to actually check the clutched pulley operation... spraying it with something solvent-based will wash out the permanent lube and send it to an early grave, if it's not dead already.

I prefer to pull the serp belt and check for proper operation with the belt disconnected... others just poke at the internal alternator fan blade with a screwdriver.

Even before that, however, I'd recommend hooking up a voltmeter to the battery and seeing what the alternator is actually doing with the car off, car on but red light on, and then car on and red light off. The idiot light is aptly named.

I sprayed pb blaster in it to see if I could make it grab and to preserve it, not to fix it.

Someone correct me if I'm wrong but isn't the one way clutch a dry system? It should have a sealed bearing but are the teeth or fingers of the one way clutch lubricated?

Sent from my Pixel XL using Tapatalk

I doubt very much that it is the clutch -- if it IS, it will make a nasty noise while ratcheting the wrong way. The clutch itself is lubricated and sealed; but if it's slipping it will make plenty of noise.

I doubt that's it; my best guess is that the "rebuilt" unit in fact has worn slip rings or brushes and is not being excited for a few seconds on start as a consequence. The one in my 03 Jetta is original, the car has more than 250k miles on it, and comes up to ~14.4V within a couple of seconds after engine start. The pulley has been replaced once during the vehicle's life.

Genesis said:

my best guess is that the "rebuilt" unit in fact has worn slip rings or brushes and is not being excited for a few seconds on start as a consequence.

Click to expand...

My guess as well.. that's what the voltmeter will help confirm.

WildChild80 said:

Someone correct me if I'm wrong but isn't the one way clutch a dry system? It should have a sealed bearing but are the teeth or fingers of the one way clutch lubricated?

Click to expand...

Clutch pawls are dry but there is a bearing, which PB Blaster will want to work its way into... that's what penetrating oil is good at doing.

Vince, I already said above that I checked the voltage and it doesn't start charging for for 6 seconds.


So if the slip rings are worn is that a big problem? Does it mean the alternator will fail? Autozone said they will be happy to exchange the unit, but it is a pain to replace.

How 'ya going about replacing them? On a Jetta it's not bad; it comes out the bottom without pulling the front clip. I can R&R an alternator in about an hour.

The basic procedure is:

1. Car on ramps, belly pan off, battery cables OFF (both), serpentine belt removed.

2. Unplug A/C clutch wire, loosen A/C mount bolts. DO NOT remove. Whack with hammer and rod to retract sleeves, remove bolts. A/C compressor drops free; set on milk crate or other support. DO NOT detach A/C hoses!

3. Unclip pax side radiator fan from FCM, unbolt spider for pax side fan, remove fan and spider.

4. Remove wires from alternator.

5. Loosen alternator bolts, DO NOT REMOVE. Use hammer and rod to whack the heads of the bolts to retract sleeves. Remove bolts. Alternator now comes out forward and down. You will have to rotate it to the correct orientation to clear but it WILL clear.

Replacement is the reverse. Fast and easy.

I figured this out when my pulley failed and although I had the tools to get it off in the car I couldn't get enough leverage. Took the alternator out and 2 minutes with my bench vise got the pulley off.

If the slip rings and/or brushes are worn it will fail. Exactly when is impossible to determine but R&Ring an alternator is easy in your garage but a royal ****** if it fails on a trip somewhere. If you take it to a stealer to have THEM do it they'll backdoor jam-job you for $1k or more for the alternator and Bentley book time, which involves removing the front clip to get it out!

Guess you didn't like my suggestion, if the light goes off after 6 seconds, it's likely a function of shotty components. Not gonna hurt the car to not charge for 6 seconds. Run it til it fails.

I did see your suggestion Bob and I did check the belt. (which is fine) I just don't want it failing on a long trip. I was just seeing if anyone would guess how long the alternator will last with this problem.

Having an exact guess is like winning the lottery. You can guess all you want but your chances are very minimal you'll get the right numbers.

Yea, no way to know that. But if I read right, you'll just put another of the same back in, might be better, might have different issue. As oilhammer points out, we've seen a lot of problems with certain replacement parts. It's of course your call, I'm of the less work school., do what you're comfortable with, and best of luck. As you say on-the-road failures are not fun.

Thanks guys. I was hoping someone had the same problem in the past and could tell me how long theirs lasted. I think that I'm going to swap it out. It will go much faster the 2nd time because I know what to do now.

EVERYONE has had a problem with low quality Autozone parts. Some of us learn from this, some don't.

My TDIs have Bosch alternators on them, no worries, no lifetime warranty, no need for it. I have probably installed several thousand of these over the years, never had a single one fail right away... they always last as long as the originals (if they were Bosch) or LONGER (if they were Valeo or Hitachi).

oilhammer said:

EVERYONE has had a problem with low quality Autozone parts. Some of us learn from this, some don't.



My TDIs have Bosch alternators on them, no worries, no lifetime warranty, no need for it. I have probably installed several thousand of these over the years, never had a single one fail right away... they always last as long as the originals (if they were Bosch) or LONGER (if they were Valeo or Hitachi).

Click to expand...

My buddy has a Mercedes shop and when the customer goes for the cheap alternator, more times than not they're back in short order getting it swapped out again, some have a warranty but the warranty usually doesn't cover labor, they usually listen to him and put a Bosch on and never regret it

Sent from my Pixel XL using Tapatalk