Bosch Alternators' Reliability

[brackenwhite]

Last summer I replaced the alternator in my '85 Carrera; it took a while but gave me a sense of accomplishment. At the same time, I installed a new Optima battery.

Recently, while I was out of the country my wife was stranded with a dead battery. On my return, I charged the car and took it for a spin. My plug-in charging monitor (plugged into cigarette lighter) indicated that the battery was discharging! The car was battery powered for who knows how long.

This wasn't the case when I first installed the alternator -- is it possible that the rebuilt units are as lousy as some say? If so, am I the 1 in a 1,000 or the 1 in 5 who experiences this?

I'm not looking forward to another educational experience in replacing the new alternator, though I'm resigned to it. Any thoughts?

Thanks

[john walker's workshop]

does the dash battery light come on with the key in the "on" position, engine not running? it needs to do that before the alt will kick into the charge mode. bosch rebuilts are what i use mostly and i've had good luck with them, in spite of being rebuilt in 3rd world countries.

[brackenwhite]

Thank you for the response. I checked and the red battery light does come on when the key is turned to the "on" position.

I'm not sure if this means that the alternator works some of the time (the lights on the monitor flickered back and forth yesterday) or if there is a loose connection somewhere in the car's electrical system. I know the battery is connected tightly.

My preliminary assessment is colored by anecdotes in earlier posts concerning Bosch reliability -- though I know there may be a number of other explanations.

Thanks again for any thoughts. . .

[mpetry]

Again, first principles - take your chassis grounds apart and apply WD-40 and wire brush - get them shiny! There are 2 - on in the front coming off the battery, and one on the engine compartment front bulkhead, connecting to the transmission.

Lightly grease everything on re-assembly and make sure that you have a good solid connection. Now retest and let us know the result.

[Laneco]

There's also a ground strap from the back of the alternator to the top of the engine. As a matter of course, when I replace an alternator I just replace that one. Figure every 20 or 30 years, it's just time to put a new one in...

angela

[brackenwhite]

Thanks Pelicans for the advice. I am going to clean up straps today and also order some new ones -- what I have looks "vintage."

I have noticed two additional symptoms that may or may not indicate something:
1) alternator light remains off when car is running, even when plug in monitor says battery is discharging. (It was on when car not running but key in "on" position.)
2) Plug-in monitor shows battery is charging for first +/-5 minutes, then begins to discharge. Perhaps a warmed connection somewhere loosens up?

Thanks and I will keep you guys updated.

[rick-l]

Originally Posted by brackenwhite

2) Plug-in monitor shows battery is charging for first +/-5 minutes, then begins to discharge.

So the voltage is around 14 and then drops to around 12?

[brackenwhite]

Closer to 13.8, then drops to 12.1.

[304065]

You have a high resistance somewhere-- check ALL connections for corrosion.

How old is the battery?

[brackenwhite]

It seems so. Battery is an Optima, +/- 1 year old.

[Wayne 962]

Hi there. These types of questions are really frustrating when they come from customers. It typically goes like this. Customer is having a problem with a particular component in his car, so he replaces it. Component works fine for a while, and then fails. Customer calls up and insists it's a defective part (particularly with electrical items). Replacement fails too within a few months. Return / failure rate from all other customers is zero. Yet the customer insists that the part is faulty and the manufacturing process is turning out bad parts.

In reality, there is something wrong with the car (or the installer). Since the customer replaced the part in the first place, then there had to be something broken or breaking with that part of the car to start with. In the case of alternators that get damaged or stop working a few months after installation, it's typically a problem with the electrical system of the car, not the replacement alternator. The fact is that it is unlikely that there would be two failures of the same part (the original one and the replacement one) - it's more likely that there's a problem with the grounding or the wiring in the car which is causing the alternator to become damaged.

I had a customer not too long ago, who insisted that the 3 headlamp switches we sent him were defective (they would burn out and fail after about 3 months). So four failures (his original one), and 200+ sold in the past year where the only ones returned were from his car, and I couldn't convince him that his car was the problem.

Very frustrating sometimes...

-Wayne

[Wayne 962]

As a followup, I would check all the grounds, and I would also be a bit suspect of the charging "monitor" that checks it through the cigarette lighter. Sometimes that's not always a very clean reading. Check the actual voltage on the battery terminals when the car is running. You also might want to have the battery tested. Some batteries, if run all the way down, become permanently damaged (unless they are deep cycle batteries). I'm not sure how the Optimas rank on that scale.

-Wayne

[brackenwhite]

Wayne, Hopefully I’m being more open minded than the headlamp switch customer.

In my most recent post, I acknowledge that the problem seems to be resistance in the system somewhere. Other threads I've read point out that resistance increases as connections/cables heat up. Makes sense. As previously stated, my ground cables look ready for antique roadshow. Perhaps the problem is the alternator though it seems more likely that +/-30 year old connections are a better bet.

Yes, my initial hypothesis was that the alternator was faulty though I qualified that by saying previous anecdotes colored this assessment. Anecdotes aren’t very scientific, I know; few of the 99.9% customers with a functioning replacement part rush to post their experience. I can see how my subject line is frustrating, perhaps in hindsight a better one may have been something like “resistance is futile.”

I really appreciate yours and all the other Pelicans' advice. Now I need to get 2 weeks of honey-do’s out of the way so I can tackle this.

[brackenwhite]

Guys,

Thanks for all the help, here’s my update.

A mechanic friend helped me check the electrical system, voltage drop was definitely at the alternator. I pulled the unit and sent in for a replacement. Connections were tight at the unit before removing.

This afternoon I put the new unit in and drove for 1-1/2 hours all over Berkeley/Oakland. No voltage drop and the system consistently charged 13.9 to 14.2v. It may have dropped slightly (closer to 13.9) toward the end.

I got a new OEM unit this time – Pelican no longer sells the rebuilt units for this application.

Glad to have my car back and hope that this fixes the problem.

Thanks again.