Hey Guys,

My alternator appears to have failed. Driving home yesterday and battery light came on and voltage was declining. Got home and battery measured 12.06 volts so I put a trickle charger on and parked car.

Looking around I see 150 amp units are around $450 but the 120 amp units are $180. Pretty big price difference. Any reason to not get the 120? Do I really need a 150?

Thanks

 

I just went through this. I personally opted for a new Bosch regulator for $50. They are a bit hard to find shipped next day, but they're out there. Search my username for more info.

Autozone will sell you a whole remanufactured unit with lifetime warranty for ~$180 IIRC, with core exchange. Perhaps not a bad deal with the stock regulators being what they are.

 

Is it common for just the regulator to fail?

 

Beware the lifetime warranties from the local chain stores. I've found out the hard way more than once that lifetime means a lifetime of swapping - especially exciting when one of them OVERvolts. They will be happy to replace the alternator but so sorry about labor and fried electronics elsewhere...

 

Yeah I've certainly been down that road. It can be hit or miss at times. My Mustang's been doing on several years now on a lifetime auto chain alternator. Ironically I had started with a really expensive aftermarket unit on the Mustang and it failed to perform at higher RPMs and the "cheapo" auto parts store unit cured the problems.

I have a big car event this weekend and must get running so I grabbed one from my local Advance Auto. $139.50 plus tax after all their online coupons, member discount codes etc. I'll see if I can get it swapped tomorrow and be back on the road. It's only a 120 amp but I don't have any aftermarket stereos etc. Heck don't even use the factory one.

 

Getting back to the OP's original question: is 120 amp OK? No. My alternator was replaced with the 120 amp instead of the 150. I didn't know there were two at the time and the place I ordered from didn't list both. 120 amp isn't enough to keep the battery charged. There is a reason the TT came with 150 amp - It is required. I have my car on a charger whenever I'm not driving it. If you go with the 120 amp, it will work fine - for about two years, then you will need a new battery (unless you charge when you are not driving). With the right amperage alternator, your battery should last 7 years or so.

 

Yes I charge my car when not driving. I have to. These cars drain the battery so fast if you don't the battery is half dead within a week and in about 2 weeks or so it won't even start. Maybe it was 3 weeks, I forget now. I just know if the car sits for about a week charger on it immediately.

 

OK this is interesting. Removing the alternator in my car now and I notice it's got a solid pulley like what is listed for automatic transmission cars. The manuals are supposed to have some sort of clutched pulley. Humm how big a deal is that? I noticed the replacement alternator I got also has a solid pulley on it.

 

While generally I agree with you, the OEM part here is not known for being a paradigm of reliability. Fortunately, it is the regulator only more often than not, and the alternator is one of the easier jobs on this car. That said, I still went for the OEM Bosch part for my repair rather then generics.

Manuals definitely have a clutched pulley. My opinion, is that it's likely a more important item the more aggressive you drive the vehicle. It also aids in feel between shifts without having as much spun up mass when the engine is deceleration. Funny cause the solid pulley means that the cars already had alternator issues in the past...back to my point above.

 

I managed to get my hands on a brand new (not remanufactured) OEM Bosch unit. The correct 150 amp with do-coupling pulley as they call it. Awesome.

I'll get it installed and test it out shortly. Curious to see if I can feel or tell any difference with a pulley that allows the alternator to free spin on hard driving and shifting.

 

New unit installed and back up and running. Went for a spirited test drive and I can't tell any difference at all. At least it's the correct unit thought. I did play with the pulley by hand prior to installing and saw how it would sort of ratchet and release when the pulley was slowed down suddenly allowing the alternator to free wheel down.

 

bummer i didnt see this thread earlier. i have a turbo alternator sitting on the shelf!

 

Doh! lol

 

Oh man doing mine tomorrow, I saw that on one of your post that you had one, just thought it would be sold by now. I order a Bosch Voltage reg but I'm going to take it down and bench test it, if it's more than the VR I'll hit you up!

 

I need to see if just my voltage regulator went out on my other unit. May have a spare myself.