Decoupler Pulley or Alternator?

[Thermo1223]

I am one to think it is the pulley but the cost of a pulley is almost what it cost for an alternator. It happened after a highway drive and battery saver came on with just 12.2v showing on the dash and dropping slowly. The only reason I made it home was probably my larger H6 AGM battery right at 11.9v, charged it overnight and same this morning on the drive to work.

As much as I want a GM OEM I need it working soon and am not willing to spend $500+

RockAuto to the rescue but the OE lasted 10 years so we'll see how the Valeo branded one does.

2015 Chevy Colorado 3.6 120k miles.

 

[Kira]

The year, make, engine and odometer reading really helps.
While the freewheel pulley might be the only part which is BROKEN, the rest of the unit might be well aged and due for a swap-out.

There's no starter/alternator rebuild shop near Easton?

 

[Thermo1223]

The year, make, engine and odometer reading really helps.
While the freewheel pulley might be the only part which is BROKEN, the rest of the unit might be well aged and due for a swap-out.

There's no starter/alternator rebuild shop near Easton?

Sorry edited. I forget not everyone sees sigs.

 

[Silverado12]

I'm assuming the alternator is for your 2015 Colorado? FWIW Valeo is an OEM parts supplier and their products are good.

 

[Thermo1223]

I'm assuming the alternator is for your 2015 Colorado? FWIW Valeo is an OEM parts supplier and their products are good.

Ya I edited it, after. Valeo never let me down before. I also had Bosch but never had the car long enough to see if it would last.

 

[Thermo1223]

Update!

It was the decoupler/clutch pulley which explains the kinda/sometimes voltage. If I had to guess it was spinning at a 1/10th it's rated speed so nowhere near enough to sustain any kind of current.

New alt installed since it was the OEM GM unit and after 10 years paying the price for a pulley when a new unit is the same cost isn't smart.

 

[zzyzzx]

I would be looking at if it's possible to replace that decoupler pulley with a normal pulley.

 

[bdc101]

Ya I edited it, after. Valeo never let me down before. I also had Bosch but never had the car long enough to see if it would last.

Bosch reportedly sold its reman alternator business to someone in China.

I learned this the hard way when I had a nice Bosch reman alternator fail on me after just a couple years of service. (This was on a BMW.) Did some research and found out all of them are crap. At least all the BMW ones.

 

[Thermo1223]

I would be looking at if it's possible to replace that decoupler pulley with a normal pulley.

I'm sure you could but with the original being 10 years old there is no guarantee the internals aren't suspect as well. I also suspect it has been going for sometime as the voltage seems way more stable now vs the last year where it would fluctuate a lot under heavy electrical loads.

 

[Trav]

Bosch reportedly sold its reman alternator business to someone in China.

I learned this the hard way when I had a nice Bosch reman alternator fail on me after just a couple years of service. (This was on a BMW.) Did some research and found out all of them are crap. At least all the BMW ones.

Bosch sold their starter and alternator business to SEG of China. If someone wants a Bosch starter or alternator for a Euro car buy the SEG it is made in original Bosch factory in Hungary for the time being, almost all the others are made in China and Mexico and reportedly lower quality (I have no personal experience with these but time will tell), the made in Hungary ones are the same quality as the original Bosch ones were.
AFAIK Bosch no longer has their own rebuilding center in MI any longer it is now in Mexico.

 

[meep]

It’s possible to use a sold pulley instead of a decoupler, but that can cause problems such as a hard downshift from the engine can leave the alternator with enough momentum to throw the belt - the decoupler allows a lower belt tensioner to be run, which prolongs belt life and bearing wear on other accessories. I’ve replaced decouplers before and it just takes a special tool to grab the snout.

 

[bdc101]

Bosch sold their starter and alternator business to SEG of China. If someone wants a Bosch starter or alternator for a Euro car buy the SEG it is made in original Bosch factory in Hungary for the time being, almost all the others are made in China and Mexico and reportedly lower quality (I have no personal experience with these but time will tell), the made in Hungary ones are the same quality as the original Bosch ones were.
AFAIK Bosch no longer has their own rebuilding center in MI any longer it is now in Mexico.

I'm still bitter about the Bosch reman that I bought for my E53 X5 which lasted exactly 3 years, maybe 12,000 miles total, and trashed my battery on its way out

 

[zzyzzx]

It’s possible to use a sold pulley instead of a decoupler, but that can cause problems such as a hard downshift from the engine can leave the alternator with enough momentum to throw the belt - the decoupler allows a lower belt tensioner to be run, which prolongs belt life and bearing wear on other accessories. I’ve replaced decouplers before and it just takes a special tool to grab the snout.

So ... somehow solid alternator pulleys that worked fine for decades are now bad???

 

[tcp71]

Porsche uses a damped tensioner for similar reason, I suspect. PDK transmission shifts are so abrupt, a simple spring action tensioner could have the belt jump off.

 

[mk378]

The decoupler is mostly to keep the alternator from overspeeding when the engine is at high rpm. This design allows higher alternator rpm at idle than a solid pulley would. Trying to second-guess the design needs to be done carefully.

 

[meep]

So ... somehow solid alternator pulleys that worked fine for decades are now bad???

Because the other things around the design have changed to optimize belt life and tension, a solid pulley has the ability to create problems. The decoupler pulley is simply a part of the system.

 

[zzyzzx]

Because the other things around the design have changed to optimize belt life and tension, a solid pulley has the ability to create problems. The decoupler pulley is simply a part of the system.

The decoupler pulley is most likely yet still another unnecessary over complication that reduces reliability for a .0001 MPG increase.

 

[zzyzzx]

The decoupler is mostly to keep the alternator from overspeeding when the engine is at high rpm. This design allows higher alternator rpm at idle than a solid pulley would. Trying to second-guess the design needs to be done carefully.

I don't do high RPM's and for something like this it's best to find someone else on the internet that has already made the improvement to a solid pulley and can verify that it's OK to do on your vehicle.

 

[Thermo1223]

The decoupler pulley is most likely yet still another unnecessary over complication that reduces reliability for a .0001 MPG increase.

It extends belt life, keeps noise down. Most new cars are barely audible when idling and is easier on everything else connected. It's a wear item like anything else.

I don't do high RPM's and for something like this it's best to find someone else on the internet that has already made the improvement to a solid pulley and can verify that it's OK to do on your vehicle.

So we should all drive at 2k RPM all day and trust someone else on the internet? Your argument is akin to not needing rubber bushings on a car because it's just for comfort and overcomplicates the suspension when metal spherical is far superior.

 

[meep]

I mean, clearly he can go to solid if he wants to. If he drives gently it shouldn’t be a problem. If he drives hard and the solid pulley allows the alternator to yank the belt hard enough to compress the tensioner, he loses the belt in traffic. And in all honesty that is probably not hugely likely - but would merely be a possibility.

If you want to go solid try it. I think we’ve explained the rationale behind it but you can certainly give it a go - depending on your use case it could be just fine.