Alternator questions...

[04PDWagon]

So last night I was driving home when i get surprised by the battery light flashing intermittently on the dash. Get home, pop the hood with the car idling and you can hear what sounded like the ac compressor cycling on and off (AC was off), but it was the alternator making the noise. Put a voltage tester on the battery and I was getting @12.4V...no charge. All of a sudden the pulsating noise goes away and the voltage reading came back up to 14.1V...charging. It stayed that way for a while. I then flipped on the high beams and the rear defroster (to load the alternator, engine running) and the pulsating came back. Has anyone experienced this before? I've had alternators die and they usually just die. None of this pulsating crap. Any ideas? I left the car at home because I didn't want the battery to run down in the middle of the turnpike so I'm likely going to try and get it resolved after work today.

 

[DIESEL DAZZLER]

battery lite

Check the over running pulley on the alternator,they start to slip and will fail and fly apart.Need special tools to remove pulley.

 

[2004Nick]

Alternator questions

And exactly what might be the "over-running pulley" if I might ask? News to me. Nick. I learn something everyday.

 

[04PDWagon]

Check the over running pulley on the alternator,they start to slip and will fail and fly apart.Need special tools to remove pulley.

Are you talking about the pulley that the serpentine belt goes over??? What other pulley would there be?

Kind of important...car has 73K miles.

 

[Keith_J]

And exactly what might be the "over-running pulley" if I might ask? News to me. Nick. I learn something everyday.

AKA sprag clutch. Reduces shudder when stopping as the alternator is turning faster at idle speed (smaller sheave diameter on alt) than a gas.

 

[kcerise]

Simlar Problem with Intermittant Grinding & battery Light

On engine start I have also noticed this behaviour with my 2003 TDI Jetta... Problem being a repeatable grind/no grind noise with the battery light coming on during the grind. At higher rpms this noise "goes away" and there is no battery light... In my case this behaviour only appears during a cold engine start up. Also worthy of mention is that with my car this only happens with the car is not warmed up. If I stop the car when it is warmed up and restart the noise / battery light scenario will not happen.

Obviously there is some type of resistance causing this -- but is this a belt slippage problem??? i.e. when the belts warm up from engine heat & friction do the quit slipping???

Any comments welcome.

 

[04PDWagon]

AKA sprag clutch. Reduces shudder when stopping as the alternator is turning faster at idle speed (smaller sheave diameter on alt) than a gas.

Does our TDI alternator have a clutch on it to vary speed??? When I was trying to figure out what was happening last night it looked to me as if the alternator was varying speed even though the car was simply idling.

 

[Keith_J]

Does our TDI alternator have a clutch on it to vary speed??? When I was trying to figure out what was happening last night it looked to me as if the alternator was varying speed even though the car was simply idling.

The clutch only allows for single direction of rotation. Alternators have significant inertial mass and the clutch allows it to "coast" when the belt velocity decreases faster than the alternator "coasts down". This reduces voltage "droops" which would happen every 180 degrees of crank rotation (30 Hz).

Actually, the car was varying the cranshaft angular velocity while the alternator was "coasting down". This is a 4 cylinder in-line engine, not too well balanced. The injection duration is but for a TINY part of the power stroke at idle and this causes great variations in the crankshaft velocity. Most of the time, the crank is "coasting" itself and there is the HUGE backwork when the cylinder under compression is compressing the charge.

What you see in the tach is the average angular velocity. If you had a means of measuring instant velocity, you would see the issue. but if you look at the belt damper while the engine is idling, all would be clear.

When the battery is low, alternator load is high, meaning there is increased torque load on the engine. The ECU compensates by longer injection pulse, meaning there is even greater deviations in crank RPM and therefore, belt velocity..

 

[04PDWagon]

Actually, the car was varying the cranshaft angular velocity while the alternator was "coasting down". This is a 4 cylinder in-line engine, not too well balanced. The injection duration is but for a TINY part of the power stroke at idle and this causes great variations in the crankshaft velocity. Most of the time, the crank is "coasting" itself and there is the HUGE backwork when the cylinder under compression is compressing the charge.

What you see in the tach is the average angular velocity. If you had a means of measuring instant velocity, you would see the issue. but if you look at the belt damper while the engine is idling, all would be clear.

When the battery is low, alternator load is high, meaning there is increased torque load on the engine. The ECU compensates by longer injection pulse, meaning there is even greater deviations in crank RPM and therefore, belt velocity..

All understood...but not what I was observing. The alternator itself would make a whining sound for about 2 seconds or so and then stop for a few seconds and then do it again and repeat the process until it mysteriously stopped. When it was making the whining noise, it looked as if the alternator was slowing down...maybe its the pulley about to fly off? At 700 RPM there'd be 23 power strokes per second...don't think my eyes are quick enough to catch the crank coasting between power strokes!

 

[Keith_J]

Sounds like you need Metalnerd's tool to remove the clutch pulley. Easiest to remove with the alternator out of the car. Meaning you have to pull the AC compressor so be careful to not damage the refrigerant hoses...or drop the compressor on your face like I did. That left a scar on my chin.

 

[04PDWagon]

Sounds like you need Metalnerd's tool to remove the clutch pulley. Easiest to remove with the alternator out of the car. Meaning you have to pull the AC compressor so be careful to not damage the refrigerant hoses...or drop the compressor on your face like I did. That left a scar on my chin.

if the clutch pulley is bad can you buy a new one and replace it or do you need to replace the whole alternator???

Although it seems that with 73K miles and the trouble it takes to remove it I'd be better off changing the whole damned thing.

 

[Keith_J]

Careful...some alternators are without the pulley. 73k miles is far from worn out. Diodes only go bad when nearly new or someone makes a mistake in jumpstarting.

The only other thing that goes bad is the regulator/brushes and that is replaceable. Unless the bearings are shot.

I had to replace mine at 140k but only due to diesel fuel getting into the brushes, wearing the outboard one excessively.

 

[Powder Hound]

The brushes are supposed to wear down, but Bosch brushes are too hard and will wear out the slip rings. So if your brushes are bad, then most likely the slip rings need replacement also, and thus, the alternator must be pulled and torn down.

As far as replacing just the pulley, with metalnerd's tool it is very straightforward. There may be a slight crack as the well torqued pulley gives, but it is doable. And, from your symptoms, it sounds like that is exactly what you need. I've never done it in the car, but it should be doable in place.

 

[oilhammer]

You need to check which alternator you have. VAG used Bosch, Hitachi, and Valeo units. They are typically interchangeable, but the Bosch ones seem to hold up the best. Although I have seen bearing failures on the Bosch units, I've seen a few Hitachis blow apart!

Hitachis typically have no serviceable parts like Bosch and Valeo do. At least not in the typical workbench sense. Bosch regular/brush sets are very easy and inexpensive to replace. This will not cause a noise, however, but a charging problem. Most of the time if a Bosch unit is making noise, it is the alternator bearings, but I would be surprised if it had this issue at only 75k miles.

I have seen more than one Hitachi alternator come apart. While I do not know what they sounded like prior to the catastrophic failure, I would think they would have made some kind of noise beforehand. One came apart so bad it sent metal bits into the timing cover, derailed the timing belt, and mashed the valvetrain...so do not dismiss the noise!

 

[TornadoRed]

The one-way pulley on 2003 alternators is a common problem. Mine failed at about 70k miles. The alternator itself lasted until 195k miles or so.

I believe that removing the alternator and then having the old pulley removed at a auto electric shop would negate the need to buy a special tool. They ought to be able to get it off for $20 or so. The replacement pulley is not expensive, but having the work done at a dealership makes the entire job quite costly.

 

[04PDWagon]

The alternator in my car is the Bosch unit. I took the car yesterday to a local VW shop owned by a couple of guys that used to work at one of the better VW dealer service departments. Of course, the whole way there and while the car was there the alternator acted 100% normal as if nothing ever happened. I turned on every conceivable electric device on the car to ensure that there was as big a load as possible...it worked normal. I left the car there for him to take it apart anyways...the alternator can be rebuilt for $100-$200 depending on what is bad and he'll charge $90 for labor. Not too shabby IMHO.

 

[oilhammer]

The alternator in my car is the Bosch unit. I took the car yesterday to a local VW shop owned by a couple of guys that used to work at one of the better VW dealer service departments. Of course, the whole way there and while the car was there the alternator acted 100% normal as if nothing ever happened. I turned on every conceivable electric device on the car to ensure that there was as big a load as possible...it worked normal. I left the car there for him to take it apart anyways...the alternator can be rebuilt for $100-$200 depending on what is bad and he'll charge $90 for labor. Not too shabby IMHO.

A Bosch reman is about $220, with a new pulley, so you are not too bad going your route at all.

 

[04PDWagon]

A Bosch reman is about $220, with a new pulley, so you are not too bad going your route at all.

Yeah I saw that up on ecstuning and tdiparts yesterday. I need the car back up and running so i need this done ASAP.

 

[04PDWagon]

Good news: Car was fixed
Bad news: Its still broken

I picked up the car yesterday and looked in the hood...still a Bosch alternator so they didn't switch it out for a POS. The casing looked like it was cleaned, the wire windings that can be seen had a different color coating that OEM, etc. You could tell that it had been worked on. Drove the car yesterday and this morning to work. Today at lunch time the battery light starts to flash again. When I pull back into the office the light stops flashing no matter what accessories I have on. I open the hood with the car idling and it sounds like metallic (as if the bearing were shot on the alternator) from the alternator. I'm 52 miles from home and further from the shop that did the repair. I now need to take the car in again.

Do you guys think that with 73K the bearings would be shot or would the pulley make this noise as well?

 

[andreigbs]

maybe you just need a new battery. if it's the original, 4-5 years is most likely the limit. if it's the kind that you can top off the cells with distilled water, that might be a solution. although you said the voltage showed 12.4 when the alternator wasn't "kicking in" and charging. maybe it can't be charged like the alternator wants and it's throwing it off. how well does the starter crank in the morning?

 

[oilhammer]

This is why I don't have anyone rebuild alternators, I just put a Bosch remanufactured unit on. Problem solved.

 

[turk90210]

re checking the clutch on the alternator (if it is fitted) I found an excellent post on a uk web site by a littledaz

"There is a check that anyone with a small amount of technical know-how can do.
1. Disconnect the battery (we don't want any thermal incidents from shorting the alternator).
2. View the alternator from above.
3. Identify the pulley end and look through the ribs of the body of the alternator.
4. Identify the alternator fan blades which can be seen through the ribs.
5. Insert a small electrical type screwdriver in between the ribs and try to turn the fan clockwise and anticlockwise.
6. If the fan turns freely in one direction and tries to move the pulley in the other it is OK.
7. If the fan tries to turn the pulley in both directions it is faulty and is causing this issue.
N.B. The fan does not require much effort to freewheel.
Another way is with the alternator removed.
Lock the alternator fan with a screwdriver or similar and try to turn the pulley in both directions.
If it freewheels in one direction it is OK

but this was in relation to noisy power steering and jerky movement

the fact the batt light is coming on in this instance indicates more towards an electrical fault (ie diode pack on the alternator or bad connection somewhere on the ind wire)
If the alternator is good but a fault lies with the ind (batt warning light wire) usually rev-ing the engine is usually good enought to excite the alternator to charge.
If when the light is flashing you check the output from the alternator and it is poor then IMO the alternator is toast

 

[04PDWagon]

Battery is 4 months old...not the culprit.

When the battery light is on, the charging voltage is 12.4...when the light is off and the car is acting normal...charging voltage is over 14V. This would indicate a problem with the alternator and/or regulator both of which should be taken care of with the rebuild. Now, if the damaged pulley can cause the alternator to not spin up to the proper speed causing it to not charge correctly then that is a different story. I need to call the shop and ask if the alt pulley was replaced as part of the rebuild.

Anyone have an idea of the average cost of said pulley?

 

[Uisge]

Anyone have an idea of the average cost of said pulley?

I know it won't apply directly to you, but I just paid $75 CAD for the pulley at the local VW Stealership.

 

[04PDWagon]

It took me a while to post this up but here goes. When the mech took the pulley out and re-checked it, it was locked. It wouldn't free spin in either direction. It seems as if it was beginning to go bad and then finally just locked up. he replaced the pulley ($42) and the car has been fine since. (knocking on wood!)

 

[andreigbs]

good to hear you're back on the road.

 

[04PDWagon]

good to hear you're back on the road.

700 miles in the accord at 23mpg and $3.13 for fuel versus 44mpg and $2.94 for diesel sucked.

 

[andreigbs]

i hear ya loud and clear; had to drive from ATL to Ft. Worth barely managing 24 mpg in a Chrysler minivan (work car) and sorely missed the mid-40s the TDI returns. why doesn't Chrysler put in the 2.7L CRD from the Jeeps and Sprinters into those minivans?

 

[mrGutWrench]

You need to check which alternator you have. VAG used Bosch, Hitachi, and Valeo units. They are typically interchangeable, but the Bosch ones seem to hold up the best. Although I have seen bearing failures on the Bosch units, I've seen a few Hitachis blow apart! (snip)

__. I didn't need to hear that! I looked at my alternator when we were doing the timing belt ("we" means that Matt "Car54" was doing the work and I was getting in his way and asking questions) and there was a Hitachi sticker on it. I'd never seen one on a Vw before so I asked if it was stock. It has 7/02 date stickers like everything else on the car so we guessed it was orig. 129K miles and OK so far.

 

[TheTDIWagonGuy]

On engine start I have also noticed this behaviour with my 2003 TDI Jetta... Problem being a repeatable grind/no grind noise with the battery light coming on during the grind. At higher rpms this noise "goes away" and there is no battery light... In my case this behaviour only appears during a cold engine start up. Also worthy of mention is that with my car this only happens with the car is not warmed up. If I stop the car when it is warmed up and restart the noise / battery light scenario will not happen.

Exact same problem with my car yesterday. Mine is an 03 with 156k km or 98k miles. It sounds like you are describing my car exactly.

Thats what I love about this site. Hear a noise, search for it, know the problem and how to fix it!